>>> python scripting

Sorting The List Elements in Python

2013-06-13T07:00:00.000+07:00

The list elements can be sorted using sort() method or sorted() function. This code shows you the difference between list's sort() method and sorted() function.

>>> # using sort() method
>>> li = [99, 28, 45, 30, 40]
>>> li.sort()
>>> li
[28, 30, 40, 45, 99]
>>> 
>>> # using sorted() function
>>> originalList = [99, 28, 45, 30, 40]
>>> sortedList = sorted(originalList)
>>> sortedList
[28, 30, 40, 45, 99]
>>> originalList
[99, 28, 45, 30, 40]
>>>

Creating Recursive Function in Python

2013-06-07T21:01:00.001+07:00

This example code shows you how to create a recursive function in Python.

>>> def factorial(num):
          if num < 0:
             print("ERROR: Invalid parameter value")
             return
          elif num == 0 or num == 1:
             return 1
          else:
             return num * factorial(num-1)
 
>>> factorial(4)
24
>>> factorial(5)
120
>>>

Defining a Class Variable in Python

2013-05-31T23:32:00.001+07:00

Class variable is a variable that is shared by all instances of a class. It is defined within a class but outside any of the class's methods. This code shows you how to define it.


>>> class Book(object):
          counter = 0    # class variable
          def __init__(self, isbn, title, author, publisher):
             Book.counter += 1
             self.isbn = isbn
             self.title = title
             self.author = author
             self.publisher = publisher
          def displayBook(self):
             print("Book #%d" % Book.counter)
             print("%s\t%s\t%s\t%s" %
                   (self.isbn,self.title,self.author,self.publisher))
		
>>> a = Book('978-0-672-32862-6','Python','David Beazley','Addison-Wesley')
>>> a.displayBook()
Book #1
978-0-672-32862-6  Python David Beazley  Addison-Wesley
>>> b = Book('978-0-321-56615-7','Objective-C','Stephen G. Kotchan','Addison-Wesley')
>>> b.displayBook()
Book #2
978-0-321-56615-7  Objective-C  Stephen G. Kotchan  Addison-Wesley
>>> c = Book('978-0-321-68056-3','Python 3','Mark Summerfield','Addison-Wesley')
>>> c.displayBook()
Book #3
978-0-321-68056-3  Python 3  Mark Summerfield  Addison-Wesley
>>>

Copying a File in Python

2013-05-30T23:50:00.000+07:00

To copy a file in Pyhton, we can use shutil.copy().

budi@linux:~$ sudo gedit test.py
[sudo] password for budi: 
budi@linux:~$ cat test.py
#!/usr/bin/python3.2

print("Hello World!")
budi@linux:~$ python3.2
Python 3.2.3 (default, Oct 19 2012, 20:13:42) 
[GCC 4.6.3] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> import os
>>> import shutil
>>> dir = os.getcwd()
>>> sourcefile = "test.py"
>>> destfile = "dest.py"
>>> shutil.copy(os.path.join(dir, sourcefile), os.path.join(dir, destfile))
>>> exit()
budi@linux:~$ cat dest.py
#!/usr/bin/python3.2

print("Hello World!")
budi@linux:~$

Displaying Thousands Separator in a Number

2013-05-29T06:37:00.000+07:00

The other way to add thousands separator in a number:

>>> def addthousandseparator(number, separator=','):
          lstr = list(str(number))
          n = len(lstr) - 3
          while n > 0:
            lstr.insert(n, separator)
            n -= 3
          return "".join(lstr)

>>> addthousandseparator(1234567)
'1,234,567'
>>> addthousandseparator(1234567890, '.')
'1.234.567.890'
>>>

Opening an URL in Python

2013-05-28T08:57:00.001+07:00

We can open an URL from Python code using open(), open_new() or open_new_tab() function on webbrowser module.

>>> import webbrowser
>>> webbrowser.open("http://www.python.org")
True
>>> webbrowser.open_new("http://www.python.org")
True
>>> webbrowser.open_new_tab("http://www.python.org")
True
>>>

Method Overloading in Python

2013-05-26T12:15:00.000+07:00

Unlike C++, Python doesn't support method overloading. To impelement this C++'s feature in Python, we can use the variable-length argument or isinstance() function. These codes show you how to implement method overloading both in C++ and Python.

budi@linux:~$ sudo gedit overload.cpp
budi@linux:~$ cat overload.cpp

/* C++ code */

#include 

class Example {
public:
  int div(int a, int b) { return a / b; }
  double div(double a, double b) { return a / b; }
};

int main() {
  Example *obj = new Example();
  std::cout<<"Integer division: "
           <<obj->div(10, 3)<<std::endl;
  std::cout<<"Floating-point division: "
           <<obj->div(10.0, 3.0)<<std::endl;
  delete obj;
  return 0;
}

budi@linux:~$ sudo g++-4.6 overload.cpp -o overload.o
budi@linux:~$ sudo chmod 755 overload.o
budi@linux:~$ ./overload.o
Integer division: 3
Floating-point division: 3.33333

budi@linux:~$ sudo gedit overload.py
budi@linux:~$ cat overload.py

#!/usr/bin/python3.2

# Python code

class Example(object):
   def __init__(self):
      pass
   def div(self, a, b):
     if isinstance(a, int) and isinstance(b, int):
        return a // b
     else:
        return a / b

if __name__ == '__main__':
   obj = Example()
   print("Integer division: ", obj.div(10, 3))
   print("Floating-point division: ", obj.div(10.0, 3.0))

budi@linux:~$ sudo chmod 755 overload.py
budi@linux:~$ ./overload.py
Integer division: 3
Floating-point division: 3.3333333333333335

Passing Variable-length Arguments

2013-05-25T21:17:00.000+07:00

This following code shows you how to pass variable-length argument in a function.

budi@linux:~$ python3.2
Python 3.2.3 (default, Oct 19 2012, 20:13:42) 
[GCC 4.6.3] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> def func(*args):
...   for i in args:
...     print(i, end=' ')
... 
>>> func(10)         # one argument
10
>>> func(10,20)      # two arguments
10 20 
>>> func(10, 20, 30) # three arguments
10 20 30 
>>>

Creating A "tar" File

2013-05-24T08:59:00.000+07:00

The following shell commands and Python codes show you how to create a tar archive file with no compression.

budi@linux:~$ cd pythoncode/
budi@linux:~/pythoncode$ ls -la
total 20
drwxr-xr-x  2 root root 4096 May 24 08:42 .
drwxr-xr-x 38 budi budi 4096 May 24 08:21 ..
-rwxr-xr-x  1 root root  714 May 24 08:23 test1.py
-rwxr-xr-x  1 root root 2143 May 24 08:22 test2.py
-rwxr-xr-x  1 root root 1429 May 24 08:22 test3.py
budi@linux:~/pythoncode$ sudo python3.2
[sudo] password for budi:
Python 3.2.3 (default, Oct 19 2012, 20:13:42) 
[GCC 4.6.3] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> import os
>>> os.getcwd()
'/home/budi/pythoncode'
>>> import tarfile, glob
>>> tfile = tarfile.open("test.tar", 'w')
>>> for filename in glob.glob("*.py"):
...    tfile.add(filename)
... 
>>> tfile.close()
>>> exit()
budi@linux:~/pythoncode$ ls -la
total 32
drwxr-xr-x  2 root root  4096 May 24 08:43 .
drwxr-xr-x 38 budi budi  4096 May 24 08:21 ..
-rwxr-xr-x  1 root root   714 May 24 08:23 test1.py
-rwxr-xr-x  1 root root  2143 May 24 08:22 test2.py
-rwxr-xr-x  1 root root  1429 May 24 08:22 test3.py
-rw-r--r--  1 root root 10240 May 24 08:45 test.tar
budi@linux:~/pythoncode$

Importing Excel File into SQLite Table

2013-05-23T13:39:00.001+07:00

The following steps show you how to import data from Excel file into SQLite table.

>>> # STEP 1: Create your Excel file
>>> import csv
>>> data = [(1,10), (2,20), (3,30), (4,40), (5,50)]
>>> with open("data.csv", 'w', newline='', encoding='utf-8') as csvfile:
          w = csv.writer(csvfile, delimiter=';')
          w.writerows(data)
          csvfile.close()
 
>>> # STEP 2: Create a table with two integer fields on your SQLite database
>>> import sqlite3
>>> conn = sqlite3.connect("sqlite3db.db")
>>> c = conn.cursor()
>>> c.execute("create table test(a integer, b integer)")
<sqlite3.Cursor object at 0x020CDE20>
>>> c.close()
>>> conn.close()
>>> 
>>> # STEP 3: Import your data.csv into test table
>>> # import csv, sqlite3
>>> with open("data.csv", 'r', newline='', encoding='utf-8') as csvfile:
          conn = sqlite3.connect("sqlite3db.db")
          c = conn.cursor()
          r = csv.reader(csvfile, delimiter=';')
          for row in r:
             c.execute("insert into test values(?,?)", (row[0], row[1]))
          conn.commit()
          csvfile.close()
 
<sqlite3.Cursor object at 0x020CDEA0>
<sqlite3.Cursor object at 0x020CDEA0>
<sqlite3.Cursor object at 0x020CDEA0>
<sqlite3.Cursor object at 0x020CDEA0>
<sqlite3.Cursor object at 0x020CDEA0>
>>> # now, check your data on the table
>>> for (a, b) in c.execute("select a, b from test"):
          print("%s\t%s" % (a, b))
 
1     10
2     20
3     30
4     40
5     50
>>> conn.close()
>>>

QH6X8NHXHVP8

Compressing Files into Zip File

2013-05-22T06:48:00.000+07:00

This code is used to compress your files into zip file.

>>> # change directory
>>> import os
>>> os.chdir("E:\\pythoncode")
>>> 
>>> # creating zip file
>>> import zipfile
>>> files = ("abs.py", "floor.py", "exp.py", "log.py", "log10.py")
>>> zf = zipfile.ZipFile("test.zip", 'w', compression=zipfile.ZIP_DEFLATED)
>>> for file in files:
          zf.write(file)
 
>>> zf.close()
>>> 
>>> 
>>> # reading data from zip file
>>> zf = zipfile.ZipFile("test.zip", 'r')
>>> for filename in zf.namelist():
          nbytes = len(zf.read(filename))
          print(filename, '\t', nbytes, " bytes")
 
abs.py      143  bytes
floor.py    199  bytes
exp.py      179  bytes
log.py      179  bytes
log10.py    194  bytes
>>> zf.close()
>>>

Exporting SQLite Table into Excel File

2013-05-21T16:50:00.000+07:00

This code illustrates how to export an SQLite table into Excel (CSV) file.

>>> import sqlite3, csv
>>> conn = sqlite3.connect(":memory:")
>>> c = conn.cursor()
>>> c.execute("create table test(c1 int, c2 int)")
<sqlite3.Cursor object at 0x0223DD20>
>>> data = [(1,10), (2,20), (3,30), (4,40), (5,50)]
>>> c.executemany("insert into test values(?,?)", data)
<sqlite3.Cursor object at 0x0223DD20>
>>> conn.commit()
>>> with open("test.csv", 'w', newline='', encoding='utf-8') as csvfile:
          w = csv.writer(csvfile, delimiter=';')
          for row in c.execute("select * from test"):
             w.writerow(row)
  
6
6
6
6
6
>>> csvfile.close()
>>> c.close()
>>> conn.close()
>>>

MySQL + Python

2013-05-20T07:29:00.000+07:00

This code shows you how to use Python with MySQL database. For this demo, the following has already been installed:

MySQL Server; it can be found here
MySQL Connector/Python; it can be found here

>>> import mysql.connector
>>> conn = mysql.connector.connect(user="budi", password="r4h4Rj0",
          host="127.0.0.1", database="pythondb")
>>> c = conn.cursor()
>>> # creating table
>>> c.execute("""
create table books(
   isbn char(17) not null,
   title varchar(50),
   author varchar(25),
   publisher varchar(25),
   constraint books_pk primary key(isbn))
""")
>>> 
>>> # inserting data into table
>>> data = [
('978-0-672-32862-6','Python Essential Reference','David Beazley','Addison-Wesley'),
('978-0-321-56615-7','Programming in Objective-C','Stephen G. Kotchan','Addison-Wesley'),
('978-0-321-68056-3','Programming in Python 3','Mark Summerfield','Addison-Wesley')]
>>> c.executemany("insert into books values(%s, %s, %s, %s)", data)
>>> conn.commit()
>>> 
>>> # performing query
>>> c.execute("select * from books")
>>> 
>>> # fetching table rows
>>> resultset = c.fetchall()
>>> for isbn, title, author, publisher in resultset:
          print("%s\t%s\t%s\t%s" % (isbn, title, author, publisher))
 
978-0-321-56615-7  Programming in Objective-C  Stephen G. Kotchan  Addison-Wesley
978-0-321-68056-3  Programming in Python 3     Mark Summerfield    Addison-Wesley
978-0-672-32862-6  Python Essential Reference  David Beazley       Addison-Wesley
>>> c.close()
>>> conn.close()
>>>

Getting File Size in Python

2013-05-20T04:47:00.000+07:00

In Python, you can get the file size using the following ways:

os.path.getsize("yourfile")

os.stat("yourfile").st_size

Example:

>>> import os
>>> os.path.getsize("E:\\pythoncode\\test.py")
13
>>> os.stat("E:\\pythoncode\\test.py").st_size
13
>>>

Listing The Files and Subdirectories in A Directory

2013-05-19T06:49:00.000+07:00

You can use this function to list all files and subdirectories in a directory.

>>> import os
>>> def ls(path):
          names = os.listdir(path)
          for name in names:
             isdir = os.path.isdir(os.path.join(path, name))
             if isdir:
               s = name + "\t\t\t<DIR>"
             else:
               s = name
             print(s)

>>> samplepath = "C:\\Python32"
>>> ls(samplepath)
django-admin.py
DLLs                    <DIR>
Doc                     <DIR>
include                 <DIR>
Lib                     <DIR>
libs                    <DIR>
LICENSE.txt
NEWS.txt
python.exe
pythonw.exe
qt.conf
README.txt
Scripts                 <DIR>
tcl                     <DIR>
Tools                   <DIR>
w9xpopen.exe
>>>

Defining Abstract Class (and Abstract Method) in Python

2013-05-18T13:47:00.000+07:00

The following code illustrates the usage of the ABC (Abstract Base Class) module.

>>> from abc import ABCMeta, abstractmethod
>>> import math
>>>
>>> # define an abstract class
>>> class Shape(metaclass=ABCMeta):
          @abstractmethod
          def area(self): pass
          @abstractmethod
          def circumference(self): pass

>>> # first descendant class
>>> class Rectangle(Shape):
           def __init__(self, w, h):
              self.width = w
              self.height = h
           # overriding Shape's area()
           def area(self):
              return self.width * self.height
           # overriding Shape's circumference()
           def circumference(self):
              return 2 * (self.width + self.height)

>>> # second descendant class
>>> class Circle(Shape):
           def __init__(self, r):
              self.radius = r
           # overriding Shape's area()
           def area(self):
              return math.pi * (self.radius ** 2)
           # overriding Shape's circumference()
           def circumference(self):
              return 2 * math.pi * self.radius

>>> # you can't create an instance of Shape class
>>> obj = Shape()
Traceback (most recent call last):
  File "", line 1, in 
    obj = Shape()
TypeError: Can’t instantiate abstract class Shape with abstract methods area, 
circumference
>>>
>>> # create an instance of Rectangle
>>> obj1 = Rectangle(5, 3)
>>> obj1.area()  # call Rectangle's area()
15
>>> obj1.circumference()
16
>>>
>>> # create an instance of Circle
>>> obj2 = Circle(3)
>>> obj2.area()  # call Circle's area()
28.274333882308138
>>> obj2.circumference()
18.84955592153876
>>>

If you're using Python 2, use this code:

>>> # define an abstract class
>>> class Shape:
          __metaclass__= ABCMeta
          @abstractmethod
          def area(self): pass
          @abstractmethod
          def circumference(self): pass

CSV (Excel) File Writing and Reading

2013-05-17T16:29:00.000+07:00

The following code shows you how to write and read data to/from a CSV (Comma Separated Values) file.

>>> import csv
>>> ################ file writing #################
>>> data = [(1, "Dennis Ritchie", "C"),
     (2, "Bjarne Stroustrup", "C++"),
     (3, "James Gosling", "Java"),
     (4, "Larry Wall", "Perl"),
     (5, "Guido Van Rossum", "Python"),
     (6, "Yukihiro Matsumoto", "Ruby")]
>>> with open("founder.csv", 'w', newline='', encoding='utf-8') as csvfile:
          w = csv.writer(csvfile, delimiter=';')
          w.writerows(data)
          csvfile.close()
 
>>> ################ file reading #################
>>> with open("founder.csv", 'r', newline='', encoding='utf-8') as csvfile:
          r = csv.reader(csvfile, delimiter=';')
          for row in r:
             for i in range(len(row)):
                print(row[i], '\t', end='')
             print()
          csvfile.close()
 
1  Dennis Ritchie     C  
2  Bjarne Stroustrup  C++  
3  James Gosling      Java  
4  Larry Wall         Perl  
5  Guido Van Rossum   Python  
6  Yukihiro Matsumoto Ruby  
>>>

Compiling Python Code into Byte Code

2013-05-17T10:40:00.000+07:00

This code shows you how to compile Python source code (.py) into Python byte code (.pyc).

>>> import os
>>> os.chdir("E:\\pythoncode")
>>> # create a new file
>>> f = open("myfile.py", 'w')
>>> f.write("""
print("Hello World!")
""")
23
>>> f.close()  # close file
>>> # import py_compile module to compile a single file
>>> import py_compile
>>> py_compile.compile("myfile.py")  # compile myfile.py
'__pycache__\\myfile.cpython-32.pyc'
>>>

Next, you can execute the .pyc file as follows:

E:\>cd pythoncode

E:\pythoncode>cd __pycache__

E:\pythoncode\__pycache__>dir
 Volume in drive E has no label.
 Volume Serial Number is 18C5-5253

 Directory of E:\pythoncode\__pycache__

17/05/2013  10:24    <DIR>          .
17/05/2013  10:24    <DIR>          ..
17/05/2013  10:24               137 myfile.cpython-32.pyc
               1 File(s)            137 bytes
               2 Dir(s)  54.142.066.688 bytes free

E:\pythoncode\__pycache__>python myfile.cpython-32.pyc
Hello World!

E:\pythoncode\__pycache__>

If you want to compile all files in a directory, use "compileall" module.

>>> import compileall
>>> mydir = os.getcwd()  # get current directory
>>> compileall.compile_dir(mydir)
Listing 'E:\\pythoncode'...
Compiling 'E:\\pythoncode\\myfile.py'...
Compiling 'E:\\pythoncode\\test.py'...
1
>>>

The print() Function Without New Line

2013-05-16T13:55:00.000+07:00

To print a string (or number) without new line, include end=' ' as argument within your print() function. Example:

>>> items = (10, 20, 30, 40, 50)
>>> for item in items:
 print(item, end=' ')
 
10 20 30 40 50 
>>>

SQLite3 + Python

2013-05-16T13:34:00.000+07:00

This code shows you how to connect SQLite3 database and Python code.

Python 3.2.3 (default, Apr 11 2012, 07:15:24) [MSC v.1500 32 bit (Intel)] on win32
Type "copyright", "credits" or "license()" for more information.
>>> import sqlite3
>>> conn = sqlite3.connect("sqlite3db.db")
>>> c = conn.cursor()
>>> c.execute("create table author (authorid integer, authorname varchar(25))")
<sqlite3.Cursor object at 0x0225DB20>
>>> data = [(1, 'David M. Beazley'), (2, 'Mark Summerfield')]
>>> c.executemany("insert into author values(?, ?)", data)
<sqlite3.Cursor object at 0x0225DB20>
>>> conn.commit()
>>> resultset = c.execute("select * from author")
>>> for authorid, authorname in resultset:
 print(authorid, '\t', authorname)
 
1   David M. Beazley
2   Mark Summerfield
>>> c.close()
>>> conn.close()
>>>

Displaying Image in Python CGI Script

2013-05-16T12:35:00.001+07:00

To display an image file using CGI script, you must place the file outside "cgi-bin" directory. If you try to access your image file directly from cgi-bin directory, you will get the "Internal Server Error" message on your web browser. You can access that file from your code as follows:

print("<img src='../images/pythonlogo.jpg'>")

Here's the complete code:

#!/usr/bin/python

print("Content-type: text/html\r\n\r\n")
print("<html>")
print("<head>")
print("<title>CGI</title>")
print("</head>")
print("<body>")
print("<img src='../images/pythonlogo.jpg' />")
print("</body>")
print("</html>")

The cmp() Function in Python 3

2013-05-15T10:16:00.001+07:00

Unlike Python 2, Python 3 doesn't provides the cmp() function. When I want to compare two dictionaries, I write a code like this:

# define function
def cmp(a, b):
   return (a.items() > b.items()) - (a.items() < b.items())

dict1 = {'one': 10, 'two': 20, 'three': 30}
dict2 = {'one': 10, 'two': 20}

print("Return value: ", cmp(dict1, dict2))

This function compares dict1 and dict2. It returns a negative number if dict1 < dict2, a positive number if dict1 > dict2, or 0 if dict1 == dict2.

BEST INFORMATIC | Bimbingan Belajar Pemrograman Sistem Cepat

2012-01-29T04:30:00.005+07:00

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BEST INFORMATIC | Bimbingan Belajar Pemrograman Sistem Cepat

http://www.best-informatic.com

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