Coding With Mj

Try Except, Raise an exception, String Formatting in Python 3.7

2020-09-13T14:28:00.009+05:30

Python Try Except:-

The try block lets you test a block of code for errors.

The except block lets you handle the error.

The finally block lets you execute code, regardless of the result of the try- and except blocks.

Exception Handling

When an error occurs, or exception as we call it, Python will normally stop and generate an error message.

These exceptions can be handled using the try statement:

Example

The try block will generate an exception, because x is not defined:

try:
  print(x)
except:
  print("An exception occurred")

Since the try block raises an error, the except block will be executed.

Without the try block, the program will crash and raise an error:

Example

This statement will raise an error, because x is not defined:

print(x)

Many Exceptions

You can define as many exception blocks as you want, e.g. if you want to execute a special block of code for a special kind of error:

Example

Print one message if the try block raises a NameError and another for other errors:

try:
  print(x)
except NameError:
  print("Variable x is not defined")
except:
  print("Something else went wrong")

Else

You can use the else keyword to define a block of code to be executed if no errors were raised:

Example

In this example, the try block does not generate any error:

try:
  print("Hello")
except:
  print("Something went wrong")
else:
  print("Nothing went wrong")

Finally

The finally block, if specified, will be executed regardless if the try block raises an error or not.

Example

try:
  print(x)
except:
  print("Something went wrong")
finally:
  print("The 'try except' is finished")

This can be useful to close objects and clean up resources:

Example

Try to open and write to a file that is not writable:

try:
  f = open("demofile.txt")
  f.write("Lorum Ipsum")
except:
  print("Something went wrong when writing to the file")
finally:
  f.close()

The program can continue, without leaving the file object open.

Raise an exception

As a Python developer you can choose to throw an exception if a condition occurs.

To throw (or raise) an exception, use the raise keyword.

Example

Raise an error and stop the program if x is lower than 0:

x = -1

if x < 0:
  raise Exception("Sorry, no numbers below zero")

The raise keyword is used to raise an exception.

You can define what kind of error to raise, and the text to print to the user.

Example

Raise a TypeError if x is not an integer:

x = "hello"

if not type(x) is int:
  raise TypeError("Only integers are allowed")

Python User Input:-

User Input

Python allows for user input.

That means we are able to ask the user for input.

The method is a bit different in Python 3.6 than Python 2.7.

Python 3.6 uses the input() method.

Python 2.7 uses the raw_input() method.

The following example asks for the username, and when you entered the username, it gets printed on the screen:

Python 3.7

username = input("Enter username:")
print("Username is: " + username)

Python String Formatting:-

To make sure a string will display as expected, we can format the result with the format() method.

String format()

The format() method allows you to format selected parts of a string.

Sometimes there are parts of a text that you do not control, maybe they come from a database, or user input?

To control such values, add placeholders (curly brackets {}) in the text, and run the values through the format() method:

Example

Add a placeholder where you want to display the price:

price = 49
txt = "The price is {} dollars"
print(txt.format(price))

You can add parameters inside the curly brackets to specify how to convert the value:

Example

Format the price to be displayed as a number with two decimals:

txt = "The price is {:.2f} dollars"

Multiple Values

If you want to use more values, just add more values to the format() method:

print(txt.format(price, itemno, count))

Example

quantity = 3
itemno = 567
price = 49
myorder = "I want {} pieces of item number {} for {:.2f} dollars."
print(myorder.format(quantity, itemno, price))

Index Numbers

You can use index numbers (a number inside the curly brackets {0}) to be sure the values are placed in the correct placeholders:

Example

quantity = 3
itemno = 567
price = 49
myorder = "I want {0} pieces of item number {1} for {2:.2f} dollars."
print(myorder.format(quantity, itemno, price))

Named Indexes

You can also use named indexes by entering a name inside the curly brackets {carname}, but then you must use names when you pass the parameter values txt.format(carname = "Ford"):

Example

myorder = "I have a {carname}, it is a {model}."
print(myorder.format(carname = "Ford", model = "Mustang"))

Python PIP

2020-09-13T14:21:00.000+05:30

Python PIP:-

What is PIP?

PIP is a package manager for Python packages, or modules if you like.

Note: If you have Python version 3.4 or later, PIP is included by default.

What is a Package?

A package contains all the files you need for a module.

Modules are Python code libraries you can include in your project.

Check if PIP is Installed

Navigate your command line to the location of Python's script directory, and type the following:

Example

Check PIP version:

C:\Users\Your Name\AppData\Local\Programs\Python\Python36-32\Scripts>pip --version

Install PIP

If you do not have PIP installed, you can download and install it from this page: https://pypi.org/project/pip/.

Download a Package

Downloading a package is very easy.

Open the command line interface and tell PIP to download the package you want.

Navigate your command line to the location of Python's script directory, and type the following:

Example

Download a package named "camelcase":

C:\Users\Your Name\AppData\Local\Programs\Python\Python36-32\Scripts>pip install camelcase

Now you have downloaded and installed your first package!

Using a Package

Once the package is installed, it is ready to use.

Import the "camelcase" package into your project.

Example

Import and use "camelcase":

import camelcase
c = camelcase.CamelCase()
txt = "hello world"
print(c.hump(txt))

Find Packages

Find more packages at https://pypi.org/.

Remove a Package

Use the uninstall command to remove a package:

Example

Uninstall the package named "camelcase":

C:\Users\Your Name\AppData\Local\Programs\Python\Python36-32\Scripts>pip uninstall camelcase

The PIP Package Manager will ask you to confirm that you want to remove the camelcase package:

Uninstalling camelcase-02.1:
  Would remove:
    c:\users\Your Name\appdata\local\programs\python\python36-32\lib\site-packages\camecase-0.2-py3.6.egg-info
    c:\users\Your Name\appdata\local\programs\python\python36-32\lib\site-packages\camecase\*
Proceed (y/n)?

Press y and the package will be removed.

List Packages

Use the list command to list all the packages installed on your system:

Example

List installed packages:

C:\Users\Your Name\AppData\Local\Programs\Python\Python36-32\Scripts>pip list

Result:

Package         Version
-----------------------
camelcase       0.2
mysql-connector 2.1.6
pip             18.1
pymongo         3.6.1
setuptools      39.0.1

findall, search, split, sub Function in Python 3.7

2020-09-13T14:15:00.001+05:30

The findall() Function

The findall() function returns a list containing all matches.

Example

Print a list of all matches:

import re

txt = "The rain in Spain"
x = re.findall("ai", txt)
print(x)

The list contains the matches in the order they are found.

If no matches are found, an empty list is returned:

Example

Return an empty list if no match was found:

import re

txt = "The rain in Spain"
x = re.findall("Portugal", txt)
print(x)

The search() Function

The search() function searches the string for a match, and returns a Match object if there is a match.

If there is more than one match, only the first occurrence of the match will be returned:

Example

Search for the first white-space character in the string:

import re

txt = "The rain in Spain"
x = re.search("\s", txt)

print("The first white-space character is located in position:", x.start())

If no matches are found, the value None is returned:

Example

Make a search that returns no match:

import re

txt = "The rain in Spain"
x = re.search("Portugal", txt)
print(x)

The split() Function

The split() function returns a list where the string has been split at each match:

Example

Split at each white-space character:

import re

txt = "The rain in Spain"
x = re.split("\s", txt)
print(x)

You can control the number of occurrences by specifying the maxsplit parameter:

Example

Split the string only at the first occurrence:

import re

txt = "The rain in Spain"
x = re.split("\s", txt, 1)
print(x)

The sub() Function

The sub() function replaces the matches with the text of your choice:

Example

Replace every white-space character with the number 9:

import re

txt = "The rain in Spain"
x = re.sub("\s", "9", txt)
print(x)

You can control the number of replacements by specifying the count parameter:

Example

Replace the first 2 occurrences:

import re

txt = "The rain in Spain"
x = re.sub("\s", "9", txt, 2)
print(x)

Match Object

A Match Object is an object containing information about the search and the result.

Note: If there is no match, the value None will be returned, instead of the Match Object.

Example

Do a search that will return a Match Object:

import re

txt = "The rain in Spain"
x = re.search("ai", txt)
print(x) #this will print an object

The Match object has properties and methods used to retrieve information about the search, and the result:

.span() returns a tuple containing the start-, and end positions of the match.
.string returns the string passed into the function
.group() returns the part of the string where there was a match

Example

Print the position (start- and end-position) of the first match occurrence.

The regular expression looks for any words that start with an upper case "S":

import re

txt = "The rain in Spain"
x = re.search(r"\bS\w+", txt)
print(x.span())

Example

Print the string passed into the function:

import re

txt = "The rain in Spain"
x = re.search(r"\bS\w+", txt)
print(x.string)

Example

Print the part of the string where there was a match.

The regular expression looks for any words that start with an upper case "S":

import re

txt = "The rain in Spain"
x = re.search(r"\bS\w+", txt)
print(x.group())

Note: If there is no match, the value None will be returned, instead of the Match Object.

Metacharacters, Special Sequences, Sets in Python 3.7

2020-09-13T14:11:00.007+05:30

Metacharacters

Metacharacters are characters with a special meaning:

Character	Description	Example
[]	A set of characters	"[a-m]"
\	Signals a special sequence (can also be used to escape special characters)	"\d"
.	Any character (except newline character)	"he..o"
^	Starts with	"^hello"
$	Ends with	"world$"
*	Zero or more occurrences	"aix*"
+	One or more occurrences	"aix+"
{}	Exactly the specified number of occurrences	"al{2}"
\|	Either or	"falls\|stays"
()	Capture and group

Special Sequences

A special sequence is a \ followed by one of the characters in the list below, and has a special meaning:

Character	Description	Example
\A	Returns a match if the specified characters are at the beginning of the string	"\AThe"
\b	Returns a match where the specified characters are at the beginning or at the end of a word (the "r" in the beginning is making sure that the string is being treated as a "raw string")	r"\bain" r"ain\b"
\B	Returns a match where the specified characters are present, but NOT at the beginning (or at the end) of a word (the "r" in the beginning is making sure that the string is being treated as a "raw string")	r"\Bain" r"ain\B"
\d	Returns a match where the string contains digits (numbers from 0-9)	"\d"
\D	Returns a match where the string DOES NOT contain digits	"\D"
\s	Returns a match where the string contains a white space character	"\s"
\S	Returns a match where the string DOES NOT contain a white space character	"\S"
\w	Returns a match where the string contains any word characters (characters from a to Z, digits from 0-9, and the underscore _ character)	"\w"
\W	Returns a match where the string DOES NOT contain any word characters	"\W"
\Z	Returns a match if the specified characters are at the end of the string	"Spain\Z"

Sets

A set is a set of characters inside a pair of square brackets [] with a special meaning:

Set	Description
[arn]	Returns a match where one of the specified characters (`a`, `r`, or `n`) are present
[a-n]	Returns a match for any lower case character, alphabetically between `a` and `n`
[^arn]	Returns a match for any character EXCEPT `a`, `r`, and `n`
[0123]	Returns a match where any of the specified digits (`0`, `1`, `2`, or `3`) are present
[0-9]	Returns a match for any digit between `0` and `9`
[0-5][0-9]	Returns a match for any two-digit numbers from `00` and `59`
[a-zA-Z]	Returns a match for any character alphabetically between `a` and `z`, lower case OR upper case
[+]	In sets, `+`, `*`, `.`, `\|`, `()`, `$`,`{}` has no special meaning, so `[+]` means: return a match for any `+` character in the string

Python RegEx Module...

2020-09-13T14:09:00.005+05:30

Python RegEx:-

A RegEx, or Regular Expression, is a sequence of characters that forms a search pattern.

RegEx can be used to check if a string contains the specified search pattern.

RegEx Module

Python has a built-in package called re, which can be used to work with Regular Expressions.

Import the re module:

import re

RegEx in Python

When you have imported the re module, you can start using regular expressions:

Example

Search the string to see if it starts with "The" and ends with "Spain":

import re

txt = "The rain in Spain"
x = re.search("^The.*Spain$", txt)

RegEx Functions

The re module offers a set of functions that allows us to search a string for a match:

Function	Description
findall	Returns a list containing all matches
search	Returns a Match object if there is a match anywhere in the string
split	Returns a list where the string has been split at each match
sub	Replaces one or many matches with a string

Modules in Python

2020-09-13T12:45:00.002+05:30

What is a Module?

Consider a module to be the same as a code library.

A file containing a set of functions you want to include in your application.

Create a Module:-

To create a module just save the code you want in a file with the file extension .py:

Example

Save this code in a file named mymodule.py

def greeting(name):
print("Hello, " + name)

Use a Module:-

Now we can use the module we just created, by using the import statement:

Example

Import the module named mymodule, and call the greeting function:

import mymodule

mymodule.greeting("Jonathan")

Note: When using a function from a module, use the syntax: module_name.function_name.

Variables in Module

The module can contain functions, as already described, but also variables of all types (arrays, dictionaries, objects etc):

Example

Save this code in the file mymodule.py

person1 = {
  "name": "John",
  "age": 36,
  "country": "Norway"
}

Example

Import the module named mymodule, and access the person1 dictionary:

import mymodule

a = mymodule.person1["age"]
print(a)

Python Datetime:-

A date in Python is not a data type of its own, but we can import a module named datetime to work with dates as date objects.

Example

Import the datetime module and display the current date:

import datetime

x = datetime.datetime.now()
print(x)

Date Output:-

When we execute the code from the example above the result will be:

2020-08-13 12:30:24.912671

The date contains year, month, day, hour, minute, second, and microsecond.

The datetime module has many methods to return information about the date object.

Here are a few examples, you will learn more about them later in this chapter:

Example

Return the year and name of weekday:

import datetime

x = datetime.datetime.now()
print(x.year)
print(x.strftime("%A"))

Creating Date Objects

To create a date, we can use the datetime() class (constructor) of the datetime module.

The datetime() class requires three parameters to create a date: year, month, day.

Example

Create a date object:

import datetime
x = datetime.datetime(2020, 5, 17)
print(x)

The datetime() class also takes parameters for time and timezone (hour, minute, second, microsecond, tzone), but they are optional, and has a default value of 0, (None for timezone).

The strftime() Method

The datetime object has a method for formatting date objects into readable strings.

The method is called strftime(), and takes one parameter, format, to specify the format of the returned string:

Example

Display the name of the month:

import datetime
x = datetime.datetime(2018, 6, 1)
print(x.strftime("%B"))

A reference of all the legal format codes:

Directive	Description	Example
%a	Weekday, short version	Wed
%A	Weekday, full version	Wednesday
%w	Weekday as a number 0-6, 0 is Sunday	3
%d	Day of month 01-31	31
%b	Month name, short version	Dec
%B	Month name, full version	December
%m	Month as a number 01-12	12
%y	Year, short version, without century	18
%Y	Year, full version	2018
%H	Hour 00-23	17
%I	Hour 00-12	05
%p	AM/PM	PM
%M	Minute 00-59	41
%S	Second 00-59	08
%f	Microsecond 000000-999999	548513
%z	UTC offset	+0100
%Z	Timezone	CST
%j	Day number of year 001-366	365
%U	Week number of year, Sunday as the first day of week, 00-53	52
%W	Week number of year, Monday as the first day of week, 00-53	52
%c	Local version of date and time	Mon Dec 31 17:41:00 2018
%x	Local version of date	12/31/18
%X	Local version of time	17:41:00
%%	A % character	%

Python Math:-

Python has a set of built-in math functions, including an extensive math module, that allows you to perform mathematical tasks on numbers.

Built-in Math Functions:-

The min() and max() functions can be used to find the lowest or highest value in an iterable:

Example

x = min(5, 10, 25)
y = max(5, 10, 25)

print(x)
print(y)

The abs() function returns the absolute (positive) value of the specified number:

Example

x = abs(-7.25)
print(x)

The pow(x, y) function returns the value of x to the power of y (xy).

Example

Return the value of 4 to the power of 3 (same as 4 * 4 * 4):

x = pow(4, 3)
print(x)

The Math Module

Python has also a built-in module called math, which extends the list of mathematical functions.

To use it, you must import the math module:

import math

When you have imported the math module, you can start using methods and constants of the module.

The math.sqrt() method for example, returns the square root of a number:

Example

import math

x = math.sqrt(64)
print(x)

The math.ceil() method rounds a number upwards to its nearest integer, and the math.floor() method rounds a number downwards to its nearest integer, and returns the result:

Example

import math

x = math.ceil(1.4)
y = math.floor(1.4)
print(x) # returns 2
print(y) # returns 1

The math.pi constant, returns the value of PI (3.14...):

Example

import math

x = math.pi
print(x)

Python JSON:-

JSON is a syntax for storing and exchanging data.

JSON is text, written with JavaScript object notation.

JSON in Python

Python has a built-in package called json, which can be used to work with JSON data.

Example

Import the json module:

import json

Parse JSON - Convert from JSON to Python

If you have a JSON string, you can parse it by using the json.loads() method.

The result will be a Python dictionary.

Example

Convert from JSON to Python:

import json

# some JSON:
x =  '{ "name":"John", "age":30, "city":"New York"}'
# parse x:
y = json.loads(x)
# the result is a Python dictionary:
print(y["age"])

Convert from Python to JSON

If you have a Python object, you can convert it into a JSON string by using the json.dumps() method.

Example

Convert from Python to JSON:

import json

# a Python object (dict):
x = {
  "name": "John",
  "age": 30,
  "city": "New York"
}
# convert into JSON:
y = json.dumps(x)
# the result is a JSON string:
print(y)

Python Classes and Objects

2020-09-13T12:36:00.002+05:30

Python Classes/Objects:-

Python is an object oriented programming language.

Almost everything in Python is an object, with its properties and methods.

A Class is like an object constructor, or a "blueprint" for creating objects.

Create a Class:-

To create a class, use the keyword class:

Example

Create a class named MyClass, with a property named x:

class MyClass:
  x = 5

Create Object:-

Now we can use the class named MyClass to create objects:

Example

Create an object named p1, and print the value of x:

p1 = MyClass()
print(p1.x)

The init() Function:-

The examples above are classes and objects in their simplest form, and are not really useful in real life applications.

To understand the meaning of classes we have to understand the built-in __init__() function.

All classes have a function called __init__(), which is always executed when the class is being initiated.

Use the __init__() function to assign values to object properties, or other operations that are necessary to do when the object is being created:

Example

Create a class named Person, use the __init__() function to assign values for name and age:

class Person:
  def __init__(self, name, age):
    self.name = name
    self.age = age

p1 = Person("John", 36)

print(p1.name)
print(p1.age)

Note: The __init__() function is called automatically every time the class is being used to create a new object.

Object Methods:-

Objects can also contain methods. Methods in objects are functions that belong to the object.

Let us create a method in the Person class:

Example

Insert a function that prints a greeting, and execute it on the p1 object:

class Person:
  def __init__(self, name, age):
    self.name = name
    self.age = age

  def myfunc(self):
    print("Hello my name is " + self.name)

p1 = Person("John", 36)
p1.myfunc()

Note: The self parameter is a reference to the current instance of the class, and is used to access variables that belong to the class.

The self Parameter:-

The self parameter is a reference to the current instance of the class and is used to access variables that belong to the class.

It does not have to be named self , you can call it whatever you like, but it has to be the first parameter of any function in the class:

Example

Use the words mysillyobject and abc instead of self:

class Person:
  def __init__(mysillyobject, name, age):
    mysillyobject.name = name
    mysillyobject.age = age

  def myfunc(abc):
    print("Hello my name is " + abc.name)

p1 = Person("John", 36)
p1.myfunc()

Modify Object Properties:-

You can modify properties on objects like this:

Example

Set the age of p1 to 40:

p1.age = 40

Delete Object Properties:-

You can delete properties on objects by using the del keyword:

Example

Delete the age property from the p1 object:

del p1.age

Delete Objects:-

You can delete objects by using the del keyword:

Example

Delete the p1 object:

del p1

The pass Statement:-

class definitions cannot be empty, but if you for some reason have a class definition with no content, put in the pass statement to avoid getting an error.

Example

class Person:
  pass

Python Inheritance:-

Inheritance allows us to define a class that inherits all the methods and properties from another class.

Parent class is the class being inherited from, also called base class.

Child class is the class that inherits from another class, also called derived class.

Create a Parent Class

Any class can be a parent class, so the syntax is the same as creating any other class:

Example

Create a class named Person, with firstname and lastname properties, and a printname method:

class Person:
  def __init__(self, fname, lname):
    self.firstname = fname
    self.lastname = lname

  def printname(self):
    print(self.firstname, self.lastname)

#Use the Person class to create an object, and then execute the printname method:

x = Person("John", "Doe")
x.printname()

Create a Child Class:-

To create a class that inherits the functionality from another class, send the parent class as a parameter when creating the child class:

Example

Create a class named Student, which will inherit the properties and methods from the Person class:

class Student(Person):
  pass

Note: Use the pass keyword when you do not want to add any other properties or methods to the class.

Now the Student class has the same properties and methods as the Person class.

Example

Use the Student class to create an object, and then execute the printname method:

x = Student("Mike", "Olsen")
x.printname()

Add the init() Function:-

So far we have created a child class that inherits the properties and methods from its parent.

We want to add the __init__() function to the child class (instead of the pass keyword).

Note: The __init__() function is called automatically every time the class is being used to create a new object.

Example

Add the __init__() function to the Student class:

class Student(Person):
  def __init__(self, fname, lname):
    #add properties etc.

When you add the __init__() function, the child class will no longer inherit the parent's __init__() function.

Note: The child's __init__() function overrides the inheritance of the parent's __init__() function.

To keep the inheritance of the parent's __init__() function, add a call to the parent's __init__() function:

Example

class Student(Person):
  def __init__(self, fname, lname):
    Person.__init__(self, fname, lname)

Now we have successfully added the __init__() function, and kept the inheritance of the parent class, and we are ready to add functionality in the __init__() function.

Use the super() Function:-

Python also has a super() function that will make the child class inherit all the methods and properties from its parent:

Example

class Student(Person):
  def __init__(self, fname, lname):
    super().__init__(fname, lname)

By using the super() function, you do not have to use the name of the parent element, it will automatically inherit the methods and properties from its parent.

Add Properties:-

Example

Add a property called graduationyear to the Student class:

class Student(Person):
  def __init__(self, fname, lname):
    super().__init__(fname, lname)
    self.graduationyear = 2019

In the example below, the year 2019 should be a variable, and passed into the Student class when creating student objects. To do so, add another parameter in the __init__() function:

Example

Add a year parameter, and pass the correct year when creating objects:

class Student(Person):
  def __init__(self, fname, lname, year):
    super().__init__(fname, lname)
    self.graduationyear = year

x = Student("Mike", "Olsen", 2019)

Add Methods:-

Example

Add a method called welcome to the Student class:

class Student(Person):
  def __init__(self, fname, lname, year):
    super().__init__(fname, lname)
    self.graduationyear = year

  def welcome(self):
    print("Welcome", self.firstname, self.lastname, "to the class of", self.graduationyear)

If you add a method in the child class with the same name as a function in the parent class, the inheritance of the parent method will be overridden.

Python Arrays and Array Methods...

2020-09-13T12:32:00.004+05:30

Python Arrays:-

Note: This page shows you how to use LISTS as ARRAYS, however, to work with arrays in Python you will have to import a library, like the NumPy library.

Arrays are used to store multiple values in one single variable:

Example

Create an array containing car names:

cars = ["Ford", "Volvo", "BMW" , "lamborghini"]

What is an Array?

An array is a special variable, which can hold more than one value at a time.

If you have a list of items (a list of car names, for example), storing the cars in single variables could look like this:

car1 = "Ford"
car2 = "Volvo"
car3 = "BMW"
car4 = "lamborghini"

However, what if you want to loop through the cars and find a specific one? And what if you had not 3 cars, but 300?

The solution is an array!

An array can hold many values under a single name, and you can access the values by referring to an index number.

Adding Array Elements:-

You can use the append() method to add an element to an array.

Example

Add one more element to the cars array:

cars.append("Honda")

Removing Array Elements:-

You can use the pop() method to remove an element from the array.

Example

Delete the second element of the cars array:

cars.pop(1)

Array Methods:-

Python has a set of built-in methods that you can use on lists/arrays.

Method	Description
append()	Adds an element at the end of the list
clear()	Removes all the elements from the list
copy()	Returns a copy of the list
count()	Returns the number of elements with the specified value
extend()	Add the elements of a list (or any iterable), to the end of the current list
index()	Returns the index of the first element with the specified value
insert()	Adds an element at the specified position
pop()	Removes the element at the specified position
remove()	Removes the first item with the specified value
reverse()	Reverses the order of the list
sort()	Sorts the list

Recursion and Lambda function in Python 3.7

2020-09-13T12:29:00.001+05:30

Recursion:-

Python also accepts function recursion, which means a defined function can call itself.

Recursion is a common mathematical and programming concept. It means that a function calls itself. This has the benefit of meaning that you can loop through data to reach a result.

The developer should be very careful with recursion as it can be quite easy to slip into writing a function which never terminates, or one that uses excess amounts of memory or processor power. However, when written correctly recursion can be a very efficient and mathematically-elegant approach to programming.

In this example, tri_recursion() is a function that we have defined to call itself ("recurse"). We use the k variable as the data, which decrements (-1) every time we recurse. The recursion ends when the condition is not greater than 0 (i.e. when it is 0).

To a new developer it can take some time to work out how exactly this works, best way to find out is by testing and modifying it.

Example

Recursion Example

def tri_recursion(k):
  if(k > 0):
    result = k + tri_recursion(k - 1)
    print(result)
  else:
    result = 0
  return result

print("\n\nRecursion Example Results")
tri_recursion(6)

Python Lambda:-

A lambda function is a small anonymous function.

A lambda function can take any number of arguments, but can only have one expression.

Syntax:-

lambda arguments : expression

The expression is executed and the result is returned:

Example

A lambda function that adds 10 to the number passed in as an argument, and print the result:

x = lambda a : a + 10
print(x(5))

Lambda functions can take any number of arguments:

Example

A lambda function that sums argument a, b, and c and print the result:

x = lambda a, b, c : a * b / c
print(x(5, 6, 2))

Why Use Lambda Functions?

The power of lambda is better shown when you use them as an anonymous function inside another function.

Say you have a function definition that takes one argument, and that argument will be multiplied with an unknown number:

def myfunc(n):
  return lambda a : a * n

Functions, Parameters or Arguments, Arbitrary Arguments *args, Arbitrary Keyword Arguments **kwargs in Python 3.7

2020-09-13T08:59:00.001+05:30

Python Functions:-

A function is a block of code which only runs when it is called.

You can pass data, known as parameters, into a function.

A function can return data as a result.

Creating a Function:-

In Python a function is defined using the def keyword:

Example

def my_function():
  print("Hello from a function")

Calling a Function:-

To call a function, use the function name followed by parenthesis:

Example

def my_function():
  print("Hello from a function")

my_function()

Arguments:-

Information can be passed into functions as arguments.

Arguments are specified after the function name, inside the parentheses. You can add as many arguments as you want, just separate them with a comma.

The following example has a function with one argument (fname). When the function is called, we pass along a first name, which is used inside the function to print the full name:

Example

def my_function(fname):
  print(fname + " Refsnes")

my_function("Emil")
my_function("Tobias")
my_function("Linus")

Parameters or Arguments?

The terms parameter and argument can be used for the same thing: information that are passed into a function.

From a function's perspective:

A parameter is the variable listed inside the parentheses in the function definition.

An argument is the value that is sent to the function when it is called.

Number of Arguments:-

By default, a function must be called with the correct number of arguments. Meaning that if your function expects 2 arguments, you have to call the function with 2 arguments, not more, and not less.

Example

This function expects 2 arguments, and gets 2 arguments:
def my_function(fname, lname):
print(fname + " " + lname)

my_function("Emil", "Refsnes")

Arbitrary Arguments, args:-*

If you do not know how many arguments that will be passed into your function, add a * before the parameter name in the function definition.

This way the function will receive a tuple of arguments, and can access the items accordingly:

Example

If the number of arguments is unknown, add a * before the parameter name:

def my_function(*kids):
  print("The youngest child is " + kids[2])

my_function("Emil", "Tobias", "Linus")

Keyword Arguments:-

You can also send arguments with the key = value syntax.

This way the order of the arguments does not matter.

Example

def my_function(child3, child2, child1):
  print("The youngest child is " + child3)

my_function(child1 = "Emil", child2 = "Tobias", child3 = "Linus")

*Arbitrary Keyword Arguments, **kwargs:-*

If you do not know how many keyword arguments that will be passed into your function, add two asterisk: ** before the parameter name in the function definition.

This way the function will receive a dictionary of arguments, and can access the items accordingly:

Example

If the number of keyword arguments is unknown, add a double ** before the parameter name:

def my_function(**kid):
  print("His last name is " + kid["lname"])

my_function(fname = "Tobias", lname = "Refsnes")

Default Parameter Value:-

The following example shows how to use a default parameter value.

If we call the function without argument, it uses the default value:

Example

def my_function(country = "India"):
  print("I am from " + country)

my_function("Sweden")
my_function("Norway")
my_function()
my_function("Brazil")

Passing a List as an Argument:-

You can send any data types of argument to a function (string, number, list, dictionary etc.), and it will be treated as the same data type inside the function.

E.g. if you send a List as an argument, it will still be a List when it reaches the function:

Example

def my_function(food):
  for x in food:
    print(x)

fruits = ["apple", "banana", "cherry"]

my_function(fruits)

Return Values:-

To let a function return a value, use the return statement:

Example

def my_function(x):
  return 5 * x

print(my_function(3))
print(my_function(5))
print(my_function(9))

The pass Statement:-

function definitions cannot be empty, but if you for some reason have a function definition with no content, put in the pass statement to avoid getting an error.

Example

def myfunction():
  pass

Loops in Python 3.7

2020-09-13T08:55:00.003+05:30

Python Loops:-

Python has two primitive loop commands:

while loops
for loops

The while Loop

With the while loop we can execute a set of statements as long as a condition is true.

Example

Print i as long as i is less than 6:

i = 1
while i < 6:
print(i)
i += 1

The while loop requires relevant variables to be ready, in this example we need to define an indexing variable, i, which we set to 1.

The break Statement

With the break statement we can stop the loop even if the while condition is true:

Example

Exit the loop when i is 3:

i = 1
while i < 6:
  print(i)
  if i == 3:
    break
  i += 1

The continue Statement

With the continue statement we can stop the current iteration, and continue with the next:

Example

Continue to the next iteration if i is 3:

i = 0
while i < 6:
  i += 1
  if i == 3:
    continue
  print(i)

The else Statement

With the else statement we can run a block of code once when the condition no longer is true:

Example

Print a message once the condition is false:

i = 1
while i < 6:
  print(i)
  i += 1
else:
  print("i is no longer less than 6")

Python For Loops:-

A for loop is used for iterating over a sequence (that is either a list, a tuple, a dictionary, a set, or a string).

This is less like the for keyword in other programming languages, and works more like an iterator method as found in other object-orientated programming languages.

With the for loop we can execute a set of statements, once for each item in a list, tuple, set etc.

Example

Print each fruit in a fruit list:

fruits = ["apple", "banana", "cherry"]
for x in fruits:
  print(x)

Looping Through a String:-

Even strings are iterable objects, they contain a sequence of characters:

Example

Loop through the letters in the word "banana":

for x in "banana":
  print(x)

The break Statement:-

With the break statement we can stop the loop before it has looped through all the items:

Example

Exit the loop when x is "banana":

fruits = ["apple", "banana", "cherry"]
for x in fruits:
  print(x)
  if x == "banana":
    break

The continue Statement:-

With the continue statement we can stop the current iteration of the loop, and continue with the next:

Example

Do not print banana:

fruits = ["apple", "banana", "cherry"]
for x in fruits:
  if x == "banana":
    continue
  print(x)

The range() Function:-

To loop through a set of code a specified number of times, we can use the range() function,

The range() function returns a sequence of numbers, starting from 0 by default, and increments by 1 (by default), and ends at a specified number.

Example

Using the range() function:

for x in range(6):
  print(x)

The range() function defaults to 0 as a starting value, however it is possible to specify the starting value by adding a parameter: range(2, 6), which means values from 2 to 6 (but not including 6):

Else in For Loop:-

The else keyword in a for loop specifies a block of code to be executed when the loop is finished:

Example

Print all numbers from 0 to 5, and print a message when the loop has ended:

for x in range(6):
  print(x)
else:
  print("Finally finished!")

Nested Loops:-

A nested loop is a loop inside a loop.

The "inner loop" will be executed one time for each iteration of the "outer loop":

Example

Print each adjective for every fruit:

adj = ["red", "big", "tasty"]
fruits = ["apple", "banana", "cherry"]

for x in adj:
  for y in fruits:
    print(x, y)

The pass Statement:-

for loops cannot be empty, but if you for some reason have a for loop with no content, put in the pass statement to avoid getting an error.

Example

for x in [0, 1, 2]:
  pass

If statements, Elif, Else, Short Hand If, Short Hand If ... Else, And, Or, Nested If and The pass Statement in Python 3.7

2020-09-13T08:53:00.005+05:30

Python Conditions and If statements:-

Python supports the usual logical conditions from mathematics:

Equals: a == b
Not Equals: a != b
Less than: a < b
Less than or equal to: a <= b
Greater than: a > b
Greater than or equal to: a >= b

These conditions can be used in several ways, most commonly in "if statements" and loops.

An "if statement" is written by using the if keyword.

Example

If statement:

a = 33
b = 200
if b > a:
  print("b is greater than a")

In this example we use two variables, a and b, which are used as part of the if statement to test whether b is greater than a. As a is 33, and b is 200, we know that 200 is greater than 33, and so we print to screen that "b is greater than a".

Python Elif:-

The elif keyword is pythons way of saying "if the previous conditions were not true, then try this condition".

Example

a = 33
b = 33
if b > a:
  print("b is greater than a")
elif a == b:
  print("a and b are equal")

In this example a is equal to b, so the first condition is not true, but the elif condition is true, so we print to screen that "a and b are equal".

Python Else:-

The else keyword catches anything which isn't caught by the preceding conditions.

Example

a = 200
b = 33
if b > a:
  print("b is greater than a")
elif a == b:
  print("a and b are equal")
else:
  print("a is greater than b")

In this example a is greater than b, so the first condition is not true, also the elif condition is not true, so we go to the else condition and print to screen that "a is greater than b".

Short Hand If in Python:-

If you have only one statement to execute, you can put it on the same line as the if statement.

Example

One line if statement:

if a > b: print("a is greater than b")

Short Hand If ... Else in Python:-

If you have only one statement to execute, one for if, and one for else, you can put it all on the same line:

Example

One line if else statement:

a = 2
b = 330
print("A") if a > b else print("B")

And

The and keyword is a logical operator, and is used to combine conditional statements:

Example

Test if a is greater than b, AND if c is greater than a:

a = 200
b = 33
c = 500
if a > b and c > a:
  print("Both conditions are True")

Or

The or keyword is a logical operator, and is used to combine conditional statements:

Example

Test if a is greater than b, OR if a is greater than c:

a = 200
b = 33
c = 500
if a > b or a > c:
  print("At least one of the conditions is True")

Nested If

You can have if statements inside if statements, this is called nested if statements.

Example

x = 41

if x > 10:
  print("Above ten,")
  if x > 20:
    print("and also above 20!")
  else:
    print("but not above 20.")

The pass Statement

if statements cannot be empty, but if you for some reason have an if statement with no content, put in the pass statement to avoid getting an error.

Example

a = 33
b = 200

if b > a:
  pass

Arrays, Tuple, Set, Dictionary in Python 3.7

2020-09-13T08:48:00.006+05:30

Python Collections (Arrays):-

There are four collection data types in the Python programming language:

List is a collection which is ordered and changeable. Allows duplicate members.
Tuple is a collection which is ordered and unchangeable. Allows duplicate members.
Set is a collection which is unordered and unindexed. No duplicate members.
Dictionary is a collection which is unordered, changeable and indexed. No duplicate members.

When choosing a collection type, it is useful to understand the properties of that type. Choosing the right type for a particular data set could mean retention of meaning, and, it could mean an increase in efficiency or security.

Python List:-

A list is a collection which is ordered and changeable. In Python lists are written with square brackets.

Example:-

Create a List:

thislist = ["apple", "banana", "cherry"]
print(thislist)

Python Tuple:-

A tuple is a collection which is ordered and unchangeable. In Python tuples are written with round brackets.

Example

Create a Tuple:

thistuple = ("apple", "banana", "cherry")
print(thistuple)

Python Set:-

A set is a collection that is unordered and unindexed. In Python sets are written with curly brackets.

Example

Create a Set:

thisset = {"apple", "banana", "cherry"}
print(thisset)

Python Dictionary:-

A dictionary is a collection which is unordered, changeable and indexed. In Python dictionaries are written with curly brackets, and they have keys and values.

Example

Create and print a dictionary:

thisdict = {
  "brand": "Ford",
  "model": "Mustang",
  "year": 1964
}
print(thisdict)

Python Operators

2020-09-13T08:46:00.004+05:30

Python Operators:-

Operators are used to performing operations on variables and values.

Python divides the operators in the following groups:

Arithmetic operators
Assignment operators
Comparison operators
Logical operators
Identity operators
Membership operators
Bitwise operators

Python Arithmetic Operators:-

Arithmetic operators are used with numeric values to perform common mathematical operations:

Operator	Name	Example
+	Addition	x + y
-	Subtraction	x - y
*	Multiplication	x * y
/	Division	x / y
%	Modulus	x % y
**	Exponentiation	x ** y
//	Floor division	x // y

Python Assignment Operators:-

Assignment operators are used to assign values to variables:

Operator	Example	Same As
=	x = 5	x = 5
+=	x += 3	x = x + 3
-=	x -= 3	x = x - 3
*=	x *= 3	x = x * 3
/=	x /= 3	x = x / 3
%=	x %= 3	x = x % 3
//=	x //= 3	x = x // 3
**=	x **= 3	x = x ** 3
&=	x &= 3	x = x & 3
\|=	x \|= 3	x = x \| 3
^=	x ^= 3	x = x ^ 3
>>=	x >>= 3	x = x >> 3
<<=	x <<= 3	x = x << 3

Python Comparison Operators:-

Comparison operators are used to compare two values:

Operator	Name	Example
==	Equal	x == y
!=	Not equal	x != y
>	Greater than	x > y
<	Less than	x < y
>=	Greater than or equal to	x >= y
<=	Less than or equal to	x <= y

Python Logical Operators:-

Logical operators are used to combining conditional statements:

Operator	Description	Example
and	Returns True if both statements are true	x < 5 and x < 10
or	Returns True if one of the statements is true	x < 5 or x < 4
not	Reverse the result, returns False if the result is true	not(x < 5 and x < 10)

Python Identity Operators:-

Identity operators are used to comparing the objects, not if they are equal, but if they are actually the same object, with the same memory location:

Operator	Description	Example
is	Returns True if both variables are the same object	x is y
is not	Returns True if both variables are not the same object	x is not y

Python Membership Operators:-

Membership operators are used to testing if a sequence is presented in an object:

Operator	Description	Example
in	Returns True if a sequence with the specified value is present in the object	x in y
not in	Returns True if a sequence with the specified value is not present in the object	x not in y

Python Bitwise Operators:-

Bitwise operators are used to comparing (binary) numbers:

Operator	Name	Description
&	AND	Sets each bit to 1 if both bits are 1
\|	OR	Sets each bit to 1 if one of two bits is 1
^	XOR	Sets each bit to 1 if only one of two bits is 1
~	NOT	Inverts all the bits
<<	Zero fill left shift	Shift left by pushing zeros in from the right and let the leftmost bits fall off
>>	Signed right shift	Shift right by pushing copies of the leftmost bit in from the left, and let the rightmost bits fall off

Data-Types in Python 3.7

2020-09-13T08:46:00.000+05:30

Python Data-Types:-

In programming, data type is an important concept.

Variables can store data of different types, and different types can do different things.

Python has the following data types built-in by default, in these categories:

Text Type:	`str`
Numeric Types:	`int`, `float`, `complex`
Sequence Types:	`list`, `tuple`, `range`
Mapping Type:	`dict`
Set Types:	`set`, `frozenset`
Boolean Type:	`bool`
Binary Types:	`bytes`, `bytearray`, `memoryview`

Getting the Data Type:-

You can get the data type of any object by using the type() function:

Example:-

Print the data type of the variable x:

x = 5
print(type(x))

Setting the Data Type:-

In Python, the data type is set when you assign a value to a variable:

Example	Data Type
x = "Hello World"	str
x = 20	int
x = 20.5	float
x = 1j	complex
x = ["apple", "banana", "cherry"]	list
x = ("apple", "banana", "cherry")	tuple
x = range(6)	range
x = {"name" : "John", "age" : 36}	dict
x = {"apple", "banana", "cherry"}	set
x = frozenset({"apple", "banana", "cherry"})	frozenset
x = True	bool
x = b"Hello"	bytes
x = bytearray(5)	bytearray
x = memoryview(bytes(5))	memoryview

Setting the Specific Data Type:-

If you want to specify the data type, you can use the following constructor functions:

Example	Data Type
x = str("Hello World")	str
x = int(20)	int
x = float(20.5)	float
x = complex(1j)	complex
x = list(("apple", "banana", "cherry"))	list
x = tuple(("apple", "banana", "cherry"))	tuple
x = range(6)	range
x = dict(name="John", age=36)	dict
x = set(("apple", "banana", "cherry"))	set
x = frozenset(("apple", "banana", "cherry"))	frozenset
x = bool(5)	bool
x = bytes(5)	bytes
x = bytearray(5)	bytearray
x = memoryview(bytes(5))	memoryview

Python Booleans:-

Booleans represent one of two values: True or False.

Boolean Values:-

In programming you often need to know if an expression is True or False.

You can evaluate any expression in Python, and get one of two answers, True or False.

When you compare two values, the expression is evaluated and Python returns the Boolean answer:

Example

Print a message based on whether the condition is True or False:

a = 200
b = 33

if b > a:
  print("b is greater than a")
else:
  print("b is not greater than a")

Keywords, Built-in Exceptions, Built-in Functions in Python 3.7

2020-09-13T08:40:00.006+05:30

Python Keywords:-

Python has a set of keywords that are reserved words that cannot be used as variable names, function names, or any other identifiers:

Keyword	Description
and	A logical operator
as	To create an alias
assert	For debugging
break	To break out of a loop
class	To define a class
continue	To continue to the next iteration of a loop
def	To define a function
del	To delete an object
elif	Used in conditional statements, same as else if
else	Used in conditional statements
except	Used with exceptions, what to do when an exception occurs
False	Boolean value, result of comparison operations
finally	Used with exceptions, a block of code that will be executed no matter if there is an exception or not.
for	To create a for loop
from	To import specific parts of a module
global	To declare a global variable
if	To make a conditional statement
import	To import a module
in	To check if a value is present in a list, tuple, etc.
is	To test if two variables are equal
lambda	To create an anonymous function
None	Represents a null value
nonlocal	To declare a non-local variable
not	A logical operator
or	A logical operator
pass	A null statement, a statement that will do nothing
raise	To raise an exception
return	To exit a function and return a value
True	Boolean value, result of comparison operations
try	To make a try...except statement
while	To create a while loop
with	Used to simplify exception handling
yield	To end a function returns a generator

Python Built-in Exceptions:-

The table below shows built-in exceptions that are usually raised in Python:

Exception	Description
ArithmeticError	Raised when an error occurs in numeric calculations
AssertionError	Raised when an assert statement fails
AttributeError	Raised when attribute reference or assignment fails
Exception	Base class for all exceptions
EOFError	Raised when the input() method hits an "end of file" condition (EOF)
FloatingPointError	Raised when a floating point calculation fails
GeneratorExit	Raised when a generator is closed (with the close() method)
ImportError	Raised when an imported module does not exist
IndentationError	Raised when indendation is not correct
IndexError	Raised when an index of a sequence does not exist
KeyError	Raised when a key does not exist in a dictionary
KeyboardInterrupt	Raised when the user presses Ctrl+c, Ctrl+z or Delete
LookupError	Raised when errors raised cant be found
MemoryError	Raised when a program runs out of memory
NameError	Raised when a variable does not exist
NotImplementedError	Raised when an abstract method requires an inherited class to override the method
OSError	Raised when a system related operation causes an error
OverflowError	Raised when the result of a numeric calculation is too large
ReferenceError	Raised when a weak reference object does not exist
RuntimeError	Raised when an error occurs that do not belong to any specific expections
StopIteration	Raised when the next() method of an iterator has no further values
SyntaxError	Raised when a syntax error occurs
TabError	Raised when indentation consists of tabs or spaces
SystemError	Raised when a system error occurs
SystemExit	Raised when the sys.exit() function is called
TypeError	Raised when two different types are combined
UnboundLocalError	Raised when a local variable is referenced before assignment
UnicodeError	Raised when a unicode problem occurs
UnicodeEncodeError	Raised when a unicode encoding problem occurs
UnicodeDecodeError	Raised when a unicode decoding problem occurs
UnicodeTranslateError	Raised when a unicode translation problem occurs
ValueError	Raised when there is a wrong value in a specified data type
ZeroDivisionError	Raised when the second operator in a division is zero

Python Built-in Functions:-

Python has a set of built-in functions.

Function	Description
abs()	Returns the absolute value of a number
all()	Returns True if all items in an iterable object are true
any()	Returns True if any item in an iterable object is true
ascii()	Returns a readable version of an object. Replaces none-ascii characters with escape character
bin()	Returns the binary version of a number
bool()	Returns the boolean value of the specified object
bytearray()	Returns an array of bytes
bytes()	Returns a bytes object
callable()	Returns True if the specified object is callable, otherwise False
chr()	Returns a character from the specified Unicode code.
classmethod()	Converts a method into a class method
compile()	Returns the specified source as an object, ready to be executed
complex()	Returns a complex number
delattr()	Deletes the specified attribute (property or method) from the specified object
dict()	Returns a dictionary (Array)
dir()	Returns a list of the specified object's properties and methods
divmod()	Returns the quotient and the remainder when argument1 is divided by argument2
enumerate()	Takes a collection (e.g. a tuple) and returns it as an enumerate object
eval()	Evaluates and executes an expression
exec()	Executes the specified code (or object)
filter()	Use a filter function to exclude items in an iterable object
float()	Returns a floating point number
format()	Formats a specified value
frozenset()	Returns a frozenset object
getattr()	Returns the value of the specified attribute (property or method)
globals()	Returns the current global symbol table as a dictionary
hasattr()	Returns True if the specified object has the specified attribute (property/method)
hash()	Returns the hash value of a specified object
help()	Executes the built-in help system
hex()	Converts a number into a hexadecimal value
id()	Returns the id of an object
input()	Allowing user input
int()	Returns an integer number
isinstance()	Returns True if a specified object is an instance of a specified object
issubclass()	Returns True if a specified class is a subclass of a specified object
iter()	Returns an iterator object
len()	Returns the length of an object
list()	Returns a list
locals()	Returns an updated dictionary of the current local symbol table
map()	Returns the specified iterator with the specified function applied to each item
max()	Returns the largest item in an iterable
memoryview()	Returns a memory view object
min()	Returns the smallest item in an iterable
next()	Returns the next item in an iterable
object()	Returns a new object
oct()	Converts a number into an octal
open()	Opens a file and returns a file object
ord()	Convert an integer representing the Unicode of the specified character
pow()	Returns the value of x to the power of y
print()	Prints to the standard output device
property()	Gets, sets, deletes a property
range()	Returns a sequence of numbers, starting from 0 and increments by 1 (by default)
repr()	Returns a readable version of an object
reversed()	Returns a reversed iterator
round()	Rounds a numbers
set()	Returns a new set object
setattr()	Sets an attribute (property/method) of an object
slice()	Returns a slice object
sorted()	Returns a sorted list
@staticmethod()	Converts a method into a static method
str()	Returns a string object
sum()	Sums the items of an iterator
super()	Returns an object that represents the parent class
tuple()	Returns a tuple
type()	Returns the type of an object
vars()	Returns the __dict__ property of an object
zip()	Returns an iterator, from two or more iterators

Tuple Methods, Set Methods, File Methods in Python 3.7

2020-09-13T08:33:00.002+05:30

Python Tuple Methods:-

In Python, tuples are immutables. Meaning, you cannot change items of a tuple once it is assigned. There are only two tuple methods count() and index() that a tuple object can call.

Python Tuple count()

returns count of the element in the tuple

Python Tuple index()

returns the index of the element in the tuple

Python Set Methods:-

A set is an unordered collection of items. Set items are unique and immutable. In this reference page, you will find all the methods that a set object can use.

Python frozenset()

returns immutable frozenset object

Python Set add()

adds an element to a set

Python Set clear()

remove all elements from a set

Python Set copy()

Returns Shallow Copy of a Set

Python Set difference()

Returns Difference of Two Sets

Python Set difference_update()

Updates Calling Set With Intersection of Sets

Python Set discard()

Removes an Element from The Set

Python Set intersection()

Returns Intersection of Two or More Sets

Python Set intersection_update()

Updates Calling Set With Intersection of Sets

Python Set isdisjoint()

Checks Disjoint Sets

Python Set issubset()

Checks if a Set is Subset of Another Set

Python Set issuperset()

Checks if a Set is Superset of Another Set

Python Set pop()

Removes an Arbitrary Element

Python Set remove()

removes the specified element from the set

Python Set symmetric_difference()

Returns the symmetric difference of sets

Python Set symmetric_difference_update()

Updates the Set with symmetric difference

Python Set union()

Returns the union of sets

Python Set update()

Add elements to the set

Python File Methods:-

There are various methods available with the file object. Some of them have been used in the above examples.

Here is the complete list of methods in text mode with a brief description:

Method	Description
close()	Closes an opened file. It has no effect if the file is already closed.
detach()	Separates the underlying binary buffer from the TextIOBase and returns it.
fileno()	Returns an integer number (file descriptor) of the file.
flush()	Flushes the write buffer of the file stream.
isatty()	Returns True if the file stream is interactive.
read(`n`)	Reads at most `n` characters from the file. Reads till the end of the file if it is negative or `None`.
readable()	Returns True if the file stream can be read from.
readline(`n`=-1)	Reads and returns one line from the file. Reads in at most `n` bytes if specified.
readlines(`n`=-1)	Reads and returns a list of lines from the file. Reads in at most `n` bytes/characters if specified.
seek(`offset`,`from`=`SEEK_SET`)	Changes the file position to `offset` bytes, in reference to `from` (start, current, end).
seekable()	Returns `True` if the file stream supports random access.
tell()	Returns the current file location.
truncate(`size`=`None`)	Resizes the file stream to `size` bytes. If `size` is not specified, resizes to current location.
writable()	Returns `True` if the file stream can be written to.
write(`s`)	Writes the string `s` to the file and returns the number of characters written.
writelines(`lines`)	Writes a list of `lines` to the file.

String Methods in Python 3.7

2020-09-13T08:30:00.004+05:30

Python String Methods:-

A string is a sequence of characters enclosed in quotation marks. In this reference page, you will find all the methods that a string object can call. For example, you can use the join() method to concatenate two strings.

Python String capitalize()

Converts first character to Capital Letter

Python String casefold()

converts to case folded strings

Python String center()

Pads string with the specified character

Python String count()

returns occurrences of substring in string

Python String encode()

returns encoded string of given string

Python String endswith()

Checks if String Ends with the Specified Suffix

Python String expandtabs()

Replaces Tab character With Spaces

Python String find()

Returns the index of first occurrence of substring

Python String format()

formats string into the nicer output

Python String format_map()

Formats the String Using Dictionary

Python String index()

Returns Index of Substring

Python String isalnum()

Checks Alphanumeric Character

Python String isalpha()

Checks if All Characters are Alphabets

Python String isdecimal()

Checks Decimal Characters

Python String isdigit()

Checks Digit Characters

Python String isidentifier()

Checks for Valid Identifier

Python String islower()

Checks if all Alphabets in a String are Lowercase

Python String isnumeric()

Checks Numeric Characters

Python String isprintable()

Checks Printable Character

Python String isspace()

Checks Whitespace Characters

Python String istitle()

Checks for Titlecased String

Python String isupper()

returns if all characters are uppercase characters

Python String join()

Returns a Concatenated String

Python String ljust()

returns a left-justified string of given width

Python String lower()

returns lowercased string

Python String lstrip()

Removes Leading Characters

Python String maketrans()

returns a translation table

Python String partition()

Returns a Tuple

Python String replace()

Replaces Substring Inside

Python String rfind()

Returns the Highest Index of Substring

Python String rindex()

Returns Highest Index of Substring

Python String rjust()

returns a right-justified string of given width

Python String rpartition()

Returns a Tuple

Python String rsplit()

Splits String From Right

Python String rstrip()

Removes Trailing Characters

Python String split()

Splits String from Left

Python String splitlines()

Splits String at Line Boundaries

Python String startswith()

Checks if String Starts with the Specified String

Python String strip()

Removes Both Leading and Trailing Characters

Python String swapcase()

swap uppercase characters to lowercase; vice versa

Python String title()

Returns a Title Cased String

Python String translate()

returns mapped charactered string

Python String upper()

returns uppercased string

Python String zfill()

Returns a copy of The String Padded With Zeros

Dictionary Methods in Python 3.7

2020-09-13T08:29:00.001+05:30

Python Dictionary Methods:-

A dictionary is a collection of key/value pairs. Python has various methods to work in dictionaries. In this reference page, you will find all the methods to work with dictionaries.

Python Dictionary clear()

Removes all Items

Python Dictionary copy()

Returns Shallow Copy of a Dictionary

Python Dictionary fromkeys()

creates a dictionary from given sequence

Python Dictionary get()

Returns Value of The Key

Python Dictionary items()

returns view of dictionary's (key, value) pair

Python Dictionary keys()

Returns View Object of All Keys

Python Dictionary pop()

removes and returns element having given key

Python Dictionary popitem()

Returns & Removes Latest Element From Dictionary

Python Dictionary setdefault()

Inserts Key With a Value if Key is not Present

Python Dictionary update()

Updates the Dictionary

Python Dictionary values()

returns view of all values in the dictionary

List Comprehension vs For Loop in Python 3.7

2020-09-13T08:27:00.001+05:30

List Comprehension vs For Loop in Python:-

Suppose, we want to separate the letters of the word human and add the letters as items of a list. The first thing that comes in mind would be using for loop.

Example 1: Iterating through a string Using for Loop:-

h_letters = []

for letter in 'human':
    h_letters.append(letter)

print(h_letters)

When we run the program, the output will be:

['h', 'u', 'm', 'a', 'n']

However, Python has an easier way to solve this issue using List Comprehension. List comprehension is an elegant way to define and create lists based on existing lists.

Let’s see how the above program can be written using list comprehensions.

Example 2: Iterating through a string Using List Comprehension:-

h_letters = [ letter for letter in 'human' ]
print( h_letters)

When we run the program, the output will be:-

['h', 'u', 'm', 'a', 'n']

In the above example, a new list is assigned to variable h_letters, and the list contains the items of the iterable string 'human'. We call the Print() function to receive the output.

Python List Methods:-

Python has a lot of list methods that allow us to work with lists. In this reference page, you will find all the list methods to work with Python lists. For example, if you want to add a single item to the end of the list, you can use the list.append() method.

Python List append()

Add a single element to the end of the list

Python List clear()

Removes all items from the List

Python List copy()

returns a shallow copy of the list

Python List count()

returns count of the element in the list

Python List extend()

adds iterable elements to the end of the list

Python List index()

returns the index of the element in the list

Python List insert()

insert an element to the list

Python List pop()

Removes the element at the given index

Python List remove()

Removes item from the list

Python List reverse()

reverses the list

Python List sort()

sorts elements of a list

Comment, Variable and Escape Sequence in Python 3.7

2020-09-13T08:20:00.009+05:30

Comment in Python:-

A comment has two types one is single-line comment and another is multi-line comment.

The single-line comment is denoted by "#" sign and The multi-line comment is denoted by

''' This is a comment '''.

Example:-

# This is a single line comment

print("Follow Coding With Mj....")

'''This is 
a Multiline
Comment'''

Variable in python:-

A Python variable is a reserved memory location to store values. In other words, a variable in a python program gives data to the computer for processing. Every value in Python has a datatype. Different data types in Python are Numbers, List, Tuple, Strings, Dictionary, etc. Variables can be declared by any name or even alphabets like a, aa, abc, etc.

Example:-

print("Enter the first number")
var1 = input() 

print("Enter the second number")
var2 = input()

print("Enter the third number")
var3 = input()
 
print("Enter the fourth number")
var4 = input() 

print("The sum of four number is", int(var1) + int(var2) + int(var3) + int(var4))

here var1, var2, var3, var4 is a example of variable.

Escape Sequence:-

To insert characters that are illegal in a string, use an escape character.

An escape character is a backslash \ followed by the character you want to insert.

An example of an illegal character is a double quote inside a string that is surrounded by double quotes:

Example:-

You will get an error if you use double quotes inside a string that is surrounded by double quotes:

txt = "We are the so-called "Vikings" from the north."

To fix this problem, use the escape character \":

The escape character allows you to use double quotes when you normally would not be allowed:

txt = "We are the so-called \"Vikings\" from the north."

Other escape characters used in Python:-

Escape Sequence	Description	Example
`\newline`	Backslash and newline ignored	print("line1 \ line2 \ line3") `line1 line2 line3`
`\\`	Backslash (`\`)	print("\\") `\`
`\'`	Single quote (`'`)	print('\'') `'`
`\"`	Double quote (`"`)	print("\"") `"`
`\a`	ASCII Bell (BEL)	print("\a")
`\b`	ASCII Backspace (BS)	print("Hello \b World!") `Hello World!`
`\f`	ASCII Formfeed (FF)	print("Hello \f World!") `Hello World!`
`\n`	ASCII Linefeed (LF)	print("Hello \n World!") `Hello World!`
`\r`	ASCII Carriage Return (CR)	print("Hello \r World!") `Hello World!`
`\t`	ASCII Horizontal Tab (TAB)	print("Hello \t World!") `Hello World!`
`\v`	ASCII Vertical Tab (VT)	print("Hello \v World!") `Hello World!`
`\ooo`	Character with octal value `ooo`	print("\110\145\154\154\157\40\127\157\162\154\144\41") `Hello World!`
`\xhh`	Character with hex value `hh`	print("\x48\x65\x6c\x6c\x6f\x20\x57\x6f\x72\x6c\x64\x21") `Hello World!`

Python 3.7

2020-07-28T22:40:00.051+05:30

Today we will start with python basics, python programming fundamentals, python for loop, python dictionary, python list, python class, python else if, python function, python tuple, python regular expression, python data types, python string, python range, python lambda, python split, python list comprehension, python operator, python lambda function, python read file, python comment, python sorted, python enumerate, python data structures, python try-catch, python global variables and then will touch upon some advanced level concepts in great detail.

After watching this course, you will be very successful in learning python.

This is a full python course. A python full course which covers each and every aspect of it. This Python tutorial for beginners which comes with no prerequisite whatsoever. I hope you will enjoy these.😊😊😊

Python Introduction:-

What is Python?

Python is a popular programming language. It was created by Guido van Rossum, and released in 1991.

It is used for:

web development (server-side),
software development,
mathematics,
system scripting.

What can Python do?

Python can be used on a server to create web applications.
Python can be used alongside software to create workflows.
Python can connect to database systems. It can also read and modify files.
Python can be used to handle big data and perform complex mathematics.
Python can be used for rapid prototyping, or for production-ready software development.

Why Python?

Python works on different platforms (Windows, Mac, Linux, Raspberry Pi, etc).
Python has a simple syntax similar to the English language.
Python has a syntax that allows developers to write programs with fewer lines than some other programming languages.
Python runs on an interpreter system, meaning that code can be executed as soon as it is written. This means that prototyping can be very quick.
Python can be treated in a procedural way, an object-orientated way, or a functional way.

Good to know

The most recent major version of Python is Python 3, which we shall be using in this tutorial. However, Python 2, although not being updated with anything other than security updates, is still quite popular.
In this tutorial, Python will be written in a text editor. It is possible to write Python in an Integrated Development Environment, such as Thonny, Pycharm, Netbeans, or Eclipse which are particularly useful when managing larger collections of Python files.

Python Syntax compared to other programming languages

Python was designed for readability and has some similarities to the English language with influence from mathematics.
Python uses new lines to complete a command, as opposed to other programming languages that often use semicolons or parentheses.
Python relies on indentation, using whitespace, to define scope; such as the scope of loops, functions, and classes. Other programming languages often use curly-brackets for this purpose.

We started our Python program with a print hello world.

print()- is a function which prints the text given between the double quotation

source code------------>

print("Hello world")

My First Website

2020-07-21T22:33:00.004+05:30

Today, we will start our journey from our first website to a blogger. This is one of the most used python programming frameworks for creating website backends. Its been an amazing journey. Everything you will learn in these tutorials will be based on my experience in learning web design. This is The set of tutorials that will make you realize, how easy it is to make a website with a very basic knowledge of python and HTML.

I am starting my first post with the heading of my website. I hope all of you support me😊😊😊

And source code in below...........

<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<link href="https://unpkg.com/tailwindcss@^1.0/dist/tailwind.min.css" rel="stylesheet">
<title>Coding With Mj</title>
</head>
<body>
<header class="text-gray-700 body-font">
<div class="container mx-auto flex flex-wrap p-5 flex-col md:flex-row items-center">
<a class="flex title-font font-medium items-center text-gray-900 mb-4 md:mb-0">
<svg xmlns="http://www.w3.org/2000/svg" fill="violet" stroke="currentColor"
stroke-linecap="round" stroke-linejoin="round" stroke-width="2" 
class="w-10 h-8 text-white p-2 bg-indigo-500 rounded-full" 
viewBox="0 0 24 24">
<path d="M12 2L2 7l10 5 10-5-10-5zM2 17l10 5 10-5M2 12l10 5 10-5"></path>
</svg>
<span class="ml-3 text-xl">Coding With Mj</span>
</a>
<nav class="md:mr-auto md:ml-4 md:py-1 md:pl-4 md:border-l md:border-gray-400 flex flex-wrap items-center text-base justify-center">
<a href="/"class="mr-5 hover:text-gray-900">Home</a>
<a href="/"class="mr-5 hover:text-gray-900">Images</a>
<a href="/"class="mr-5 hover:text-gray-900">Contact</a>
<a href="/"class="mr-5 hover:text-gray-900">News</a>
<a href="/"class="mr-5 hover:text-gray-900">About</a>
</nav>
<button class="inline-flex items-center bg-gray-200 
border-0 py-1 px-3 focus:outline-none 
hover:bg-gray-300 rounded text-base mt-4 md:mt-0">Search
<svg fill="none" stroke="currentColor" 
stroke-linecap="round" stroke-linejoin="round" stroke-width="2" 
class="w-4 h-4 ml-1" viewBox="0 0 24 24">
<path d="M5 12h14M12 5l7 7-7 7"></path>
</svg>
</button>
</div>
</header>
<section class="text-gray-700 body-font">
<div class="container mx-auto flex px-5 py-24 
md:flex-row flex-col items-center">
<div class="lg:flex-grow md:w-1/2 lg:pr-24 md:pr-16 flex flex-col 
md:items-start md:text-left mb-16 md:mb-0 items-center text-center">
<h1 class="title-font sm:text-4xl 
text-3xl mb-4 font-medium text-gray-900"> Share of knowledge
<br class="hidden lg:inline-block">
</h1>
<p class="mb-8 leading-relaxed"></p>
<div class="flex justify-center">
<button class="inline-flex text-white bg-indigo-500 
border-0 py-2 px-6 focus:outline-none 
hover:bg-indigo-600 rounded text-lg">Next Page</button>
<button class="ml-4 inline-flex text-gray-700 bg-gray-200 border-0 py-2 
px-6 focus:outline-none hover:bg-gray-300 rounded text-lg">Previous</button>
</div>
</div>
<div class="lg:max-w-lg lg:w-full md:w-1/2 w-5/6">
<img class="object-cover object-center rounded" alt="hero" 
src="https://source.unsplash.com/720x600/?books,knowledge ">
</div>
</div>
</section> 
</body>
</html>