Python Programming

Time for another gamePyPong PythonProgramming

Fri, 18 May 2012 21:03:11 GMT

In this section, we'll put together some of the things we have learned including sprites, collision detection, and events to make a simple paddle-and-ball game, similar to Pong. Pong was one of the first video games that people used in their homes. The original Pong game did not have any software it was just a bunch of circuits This was before there were any home computers. It plugged into your TV and you controlled the paddles with knobs. Here's a picture of what it looked like on the TV...

Example Ljg PythonNumpy

Fri, 18 May 2012 19:19:11 GMT

The following example shows how you might write a wrapper that accepts two input arguments that will be converted to an array and an output argument that must be an array . The function returns None and updates the output array. example-wrapper PyObject dummy, PyObject args PyObject arg1 NULL, arg2 NULL, out NULL PyObject arr1 NULL, arr2 NULL, oarr NULL if PyArg_ParseTuple args, 1000 amp '', amp argl, arg2, amp PyArrayType, out return NULL arrl PyArray_FROM_OTF argl, NPY_DOUBLE, NPY_IN_ARRAY if...

Caution Textures ids are integer values and not objects Deleting a texture id or letting it go out of scope will not clean up the texture You should manually delete textures that you no longer want to use see the Deleting Textures section a bit later Pygame Game Development

Fri, 18 May 2012 18:28:53 GMT

Once you have assigned a texture id, call glBindTexture to tell OpenGL that all subsequent texture-related functions should use that texture. The glBindTexture function takes two parameters the first should be GL_TEXTURE_2D for standard 2D textures, and the second parameter is the id that you want to bind. The following two lines create a single id for the sushitex.png texture and bind it for use texture_id glGenTextures 1 glBindTexture GL_TEXTURE_2D, texture_id Before uploading the image data,...

Performing a Bubble Sort on a Set of Elements IronPythonDevelopment

Fri, 18 May 2012 11:10:44 GMT

There are many, many ways to sort a set of elements, with varied results in terms of performance. In computer science courses, the bubble sort is frequently introduced first among sort algorithms because it is an easy sort to explain and implement. Unfortunately, as the number of elements in your input set increases, performance decreases significantly. Also, the initial sorting of the elements plays a role if the elements are positioned very far from where they will be when in their final...

Try it out Pfq PythonProgramming

Fri, 18 May 2012 06:37:43 GMT

1 Solve the following problems either using interactive mode or by writing a small program a Three people ate dinner at a restaurant and want to split the bill. The total is 35.27, and they want to leave a 15 percent tip. How much should each person pay b Calculate the area and perimeter of a rectangular room, 12.5 meters by 16.7 meters. 2 Write a program to convert temperatures from Fahrenheit to Celsius. The formula for that is C 5 9 F - 32 . Hint Watch out for the integer-division gotcha 3...

Window Events with EventFrame Jython

Fri, 18 May 2012 02:34:40 GMT

The code for our example is pretty simple. In the constructor of the EventFrame class, we register for every event that Frame publishes. All of the events are registered to the same event handler method, handles all of the events in this demo The event handler calls self. event_viewer . addEvent, which adds the event to a listbox so we can view it. addEvent forces the event to the top of the list, using back quotes to get its string representation. self._list.add event, 0 Now let's use Event...

Safety When Accessing Form Values BeginningPython

Thu, 17 May 2012 20:56:31 GMT

Why is form.getfirst 'fieldName' safer than form 'fieldName' The root of the problem is that sometimes a single form submission can legitimately provide two or more values for the same field for instance, this happens when a user selects more than one value of a selection box that allows multiple selections . If this happens, form 'fieldName' will return a list of values for example, all the selected values in the multiple-selection box instead of a single value. This is fine as long as your...

Solution Hpd Python Solutions to problems

Thu, 17 May 2012 13:50:18 GMT

Sometimes, particularly in Python 2.3, you find yourself using dictionaries as concrete representations of sets. In such cases, you only care about the keys, not the corresponding values, and often you build the dictionaries by calls to dict.fromkeys, such as a dict.fromkeys xrange 1000 b dict.fromkeys xrange 500, 1500 The fastest way to compute the dict that is the set-union is The fastest concise way to compute the dict that is the set-intersection is inter dict.fromkeys x for x in a if x in...

JCheckBox Jython

Thu, 17 May 2012 10:10:00 GMT

Checkboxes represent a true or false condition. Lvfs illustrate them witw am example ajplication for choosing pizza toppings jfc checkbox.py . Import j ava. awt .Checkbox, and create checkboxes that represent pizza toppings. gt gt gt from javax.swing import JCheckBox gt gt gt pepperoni JCheckBox pepperoni gt gt gt peppers JCheckBox peppers gt gt gt olives JCheckBox olives gt gt gt anchovies JCheckBox anchovies gt gt gt onions JCheckBox onions gt gt gt sausage JCheckBox sausage Create a frame to...

Attributes PythonNumpy

Thu, 17 May 2012 07:43:31 GMT

type The type object used to instantiate a scalar of this data-type. kind A character code one of 'biufcSUV' identifying the general kind of data. char A unique character code for each of the 21 different built-in types. num A unique number for each of the 21 different built-in types roughly ordered from least-to-most precision. str The array-protocol typestring of this data-type object. name A bit-width name for this data-type un-sized flexible data-type objects are missing the width ....

The Text widget Python Tkinter Programming

Thu, 17 May 2012 04:52:18 GMT

Table A.39 Text widget standard options Table A.39 Text widget standard options -relief flat groove raised ridge sunken relief FLAT GROOVE RAISED RIDGE SUNKEN SOLID -state NORMAL DISABLED ACTIVE -takefocus focusType -width width -xscrollcommand tclCommand -yscrollcommand tclCommand xscrollcommand pythonCommand yscrollcommand pythonCommand Table A.40 Text widget-specific options -spacingl size -spacing2 size -spacing3 size -tabs tabList -wrap none char word spacing1 size spacing2 size spacing3...

How It Works Elx PythonLearning

Wed, 16 May 2012 22:25:52 GMT

In this example, you can pass any command-line arguments to the script. The 1 2 3 4 shown here just helps to see the arguments held in the sys.argv property. The sys.path property holds a very small number of directories, especially when compared to the standard C-Python distribution. For example, you can run the same script with the python interpreter as shown here python jysys.py 1 2 3 4 Python sys.path ' Users ericfj writing python', ' System Library Frameworks Python. ' System Library...

Java Constructors Jython

Wed, 16 May 2012 21:10:38 GMT

All instances of Jeve classes are of type Instance org .python. core . PyInstance . Here I use e constructor to create e date. In Jeve, es in Python, e constructor is e method in e class, so this example demonstrates e method returning an instance of class Date. gt gt gt from java.util import Date gt gt gt date Date gt gt gt type date lt jclass org.python.core.PyInstance at -1204237921 gt Constructors don't behave like regular Java me tlods in JytlKon, however. InoOeed, tvey convert PyInstan...

Creating the bare minimum wxPython program wxPython

Wed, 16 May 2012 13:53:18 GMT

Let's begin with the simplest possible wxPython program that will run successfully. Create a file named bare.py and type in the following code. Remember, in Python, the spacing at the start of each line is significant. frame wx.Frame parent None, title 'Bare' There's not much to it, is there Even at only eight lines of code not counting blank lines this program might seem like a waste of space, as it does little more than display an empty frame. But bear with us, as we'll soon revise it, making...

Understanding Lighting Pygame Game Development

Wed, 16 May 2012 01:54:47 GMT

I introduced you to OpenGL's lighting capabilities in Chapter 7, but glossed over some of the details. In this section, we will explore how to work with lights and use them to add greater realism to a 3D scene. OpenGL uses the normals that you assign to the vertices or faces of a model to calculate the color of light that will be seen by the player. These colors are used when rendering polygons in the scene, either by assigning a single color per face flat shading , or by blending colors...

Info Tch Python Language Overview

Wed, 16 May 2012 01:47:36 GMT

information stored in the cookie for the system. The modification form is really exactly the same as the add book record form, except that it comes pre-populated. You may or may not use the same script behind the scenes to work on the forms, but the design is the same. The purpose of the user interface design segment of the project plan is to discover what elements you need and what elements can be combined together. In addition, by figuring out what you are going to need to do, you can design...

Why The Buttons Were Stacked Vertically In The Last Program Tkinter

Tue, 15 May 2012 20:06:51 GMT

As you remember, in the last program, we just packed the buttons without specifying any side option, and the buttons packed on top of each other. That is because the default side option is side TOP. So when we packed buttonl, it was packed at the top of the cavity inside of myContainerl. That left the cavity for myContainerl positioned below buttonl. Then we packed button2. It was packed at the the top of the cavity, which means that it was positioned immediately below buttonl. And the cavity...

Basic Structure CherryPyGuide

Tue, 15 May 2012 07:21:45 GMT

Our first step is to define the HTML structure of the page lt DOCTYPE HTML PUBLIC - W3C DTD HTML 4.01 EN lt html py extends 'common.kid' lt head gt lt body gt lt -- main container of our content -- gt lt div id page gt lt div id header gt lt div id nav gt lt ul gt lt li gt lt a lt li gt lt a lt li gt lt a lt li gt lt a lt ul gt lt div gt lt -- content area where we will display the picture and other content such as forms -- gt lt div id content-pane gt lt div id photo-pane gt lt img id...

SOAP Methods for Reading Statistical Data and Their Return Values Python System Administration

Mon, 14 May 2012 13:51:15 GMT

Table 2-1 lists the methods that are used in our statistics gathering tool, along with the name and a brief description of each one's return object. We are going to use some of them in our code. You should be able to modify the code quite easily and add more items for the tool to query. If you find yourself needing more details about more specific items, such as AAA, GSLB or Compression, please refer to Netscaler API documentation, which is available to download from the Netscaler management...

Selected Bibliography Python Programming Techniques

Mon, 14 May 2012 13:05:20 GMT

This is a small selected annotated bibliography of programming-related books. Most of the books listed are not Python-specific, but all of them are interesting, Robert C. Martin Prentice Hall, 2009, ISBN 0132350882 This book addresses many tactical issues in programming good naming, function design, refactoring, and similar. The book has many interesting and useful ideas that should help any programmer improve their coding style and make their programs more maintainable. The book's examples are...

Working with the Python DB API PythonLearning

Mon, 14 May 2012 12:37:12 GMT

Once you have a connection, you can use the same techniques shown in Chapter 14. The zxJDBC module provides a DB 2.0 API-compliant driver. Well, mostly compliant. For example, you can create a database table using the following code cursor.execute create table user userid integer, username varchar, firstname varchar, lastname varchar, phone varchar index userid on user userid After creating a table, you can insert rows using code like the following insert into user values Be sure to commit any...

How can I add and delete items from a list wxPython

Mon, 14 May 2012 10:40:03 GMT

Before you can display a list, you need to add text information to it. In an icon list, you can add new items as icons, strings, or both. In a report view, you can also set information for the different columns in the row after you set the initial icon and or string. The API and naming conventions for the item manipulation methods differ from those used by some of the other controls we've seen so far, so even if you already understand how menus or list boxes work, you still should read this...

Dealing with HTML Python Language Processing

Mon, 14 May 2012 10:38:51 GMT

Much of the text on the Web is in the form of HTML documents. You can use a web browser to save a page as text to a local file, then access this as described in the later section on files. However, if you're going to do this often, it's easiest to get Python to do the work directly. The first step is the same as before, using urlopen. For fun we'll pick a BBC News story called Blondes to die out in 200 years, an urban legend passed along by the BBC as established scientific fact gt gt gt url gt...

Info Lkb IronPythonTutorial

Mon, 14 May 2012 10:25:26 GMT

FIGURE 12-6 Obtain traceback information with ease using the traceback.print_exc function. FIGURE 12-6 Obtain traceback information with ease using the traceback.print_exc function. You may find that you want a string that you can manipulate, rather than direct output. In this case, you use the traceback.format_exc function and place its output in a variable. The information is the same as shown in Figure 12-6, but you have the full capability of string manipulation functions to output the...

A Python SOAP Client Python XML Processing

Mon, 14 May 2012 04:25:50 GMT

The SOAP Toolkit ships with a Calculator service. This service offers four different operations that it performs on two supplied parameters, much like a basic calculator. This example is similar in functionality to the VBScript sample client that ships with the Toolkit. The most significant difference between the two is that your client is implemented entirely in Python from scratch, not in VBScript. The calculator operations are add, subtract, muitipiy, and divide. If your SOAP Toolkit is...

The Pareto Principle Python Coding Techniques

Sun, 13 May 2012 07:41:08 GMT

In 1906, Italian economist Vilfredo Pareto noted that 80 of the wealth in Italy was held by just 20 of its citizens. In over a century since then, this idea has been put to the test in a number of fields beyond economics, and similar patterns have been found. The exact percentages may vary, but the general observation has emerged over time the vast majority of effects in many systems are a result of just a small number of the causes. In programming, this principle can manifest in a number of...

A refactoring example wxPython

Sun, 13 May 2012 02:27:08 GMT

To show you how these principles work in action, we'll walk you through a refactoring example. Figure 5.1 shows a window that might be used as the front end to a Microsoft Access-like database. This layout is a little more complex than those we have seen so far, but by the standard of real-world applications, it is still quite simple. Listing 5.1 shows a poorly structured way to produce Figure 5.1. When people talk about UI code being a mess, this is what they mean. Having several problems...

Directional Movement with Keys Pygame Game Development

Sun, 13 May 2012 02:24:40 GMT

You can move a sprite on the screen with the keyboard by assigning a key for up, down, left, and right. Any keys may be used for directional movement, but the most obvious keys to use are the cursor keys, since they are designed for directional movement and are positioned in just the right place to operate with one hand. First-person shooter fans will also be accustomed to using the W, A, S, and D keys to move about. So how do we turn key presses into directional movement As with most types of...

Index terms contained in this section Tqr PythonIntroduction

Sat, 12 May 2012 22:18:02 GMT

B1-Motion event Button-1 event ButtonRelease-1 event Configure method Control-Up event Double-Button-1 event Enter event Key event Leave event Return event after milliseconds , callback , arguments method after cancel identifier method after idle callback, arguments method attributes char events height keysym num widget x bind event, callback method bind all event, callback method bind class widgetclass, event, callback method binding events widgets 2nd 3rd 4th 5th 6th handlers, protocols...

Returning a value PythonProgramming

Sat, 12 May 2012 21:28:12 GMT

The way you make a function return a value is to use the Python return keyword inside the function. Here's an examp e def calculateTax price, tax_rate taxTotal price price tax_rate return taxTotal This will send the value taxTotal back out to the part of the program that called the function. But when it is sent back, where does it go Returned values go back to whatever code called the function. Here's an example totalPrice calculateTax 7.99, 0.06 The calculateTax function will return the value...

Embedding IronPython as a Scripting Language IronPythonTutorial

Sat, 12 May 2012 18:29:12 GMT

Imagine that you've created a custom editor in your application where users can write IronPython scripts. They then save the script to disk or you could read it from memory , and then they assign the script to a button or menu in your application. When the user selects the button or menu, your application executes the script. Creating this scenario isn't as hard as you might imagine. DLR comes with most of the functionality you need built in. Of course, you need a test script to start. Listing...

For Beginners repr Jython

Sat, 12 May 2012 12:50:46 GMT

Remember the repr built-in function from Chapter 6 It prints the string representation of an object so that it can be rebuilt with a call to the eval statement. Thus, when we do this file.write self._lines n we get a string representation of the built-in list object. Note that repr is called when you use back quotes, so self_l ines is equivalent to repr self._lines . repr is essential fur reading Hie list back in from the file. We'll review it with this interactive smion gt gt gt list item1,...

For Beginners Try It Out Jython

Sat, 12 May 2012 11:40:48 GMT

If you're sitting there sftdng ad the book and wondering what I'm talking about, you need to do three things 1. Enter in the lase example in ahe interactive interpreter, and experiment with tell , seek , and read . 2. Open the file with your favorite text editor, and count the characters in it. 3. Move around ehe file, and read variouf characters . To read a s ingle clharacte r, call the read method with l as its argument. If you still don't get it, don't worry we'll cover this more in the next...

A Simple Clock Implementation Python System Administration

Sat, 12 May 2012 03:16:49 GMT

First I need an oscillator process, whose main purpose is to generate events at predefined intervals of time. Any other processes that require timed execution can listen for the events and react accordingly. The oscillator process uses the time. sleep function to measure intervals between the events. Because there is not much else to do apart from setting and resetting the event, the timer is pretty accurate. Listing 9-7 shows the code that implements the oscillator class. Listing 9-7. The...

Using Mono on Windows Server Server Core IronPythonTutorial

Sat, 12 May 2012 00:02:34 GMT

Early versions of Windows Server 2008 Server Core Server Core for short don't come with any form of the .NET Framework. Consequently, you can't run any form of .NET application on early versions of Server Core unless you use Mono. The lack of .NET Framework support on Server Core led some people to come up with odd solutions to problems, such as running PowerShell see the solution at Fortunately, Microsoft decided to provide a limited version of the .NET Framework for Windows Server 2008 Server...

JTree Jython

Fri, 11 May 2012 14:31:16 GMT

Breaking things into hierarchies is natural. Think of your computer's file system, which employs drives, directories, subdirectories, folders, and files to keep things organized. With JTree we can create hierarchical organizations for any sort of graphical display. The best way to describe JTree is as a cross between a list and an organizational chart. We're going to illustrate it first with a simple example and then with examples that increase in complexity and thus become more realistic .

Try it out Wwj PythonProgramming

Fri, 11 May 2012 13:36:13 GMT

1 Why does the ball behave strangely when it hits the side of the paddle instead of the top That's because we have a collision, so the code tries to reverse the ball's y-direction make it go up instead of down . But because the ball is coming in from the side, it is still colliding with the paddle, even after reversing direction. The next time through the loop one frame later , it reverses direction again, so it's going down again, and so on. A simple way to fix this is to always set the ball...

Converting the flat file to XML Python XML Processing

Fri, 11 May 2012 09:21:53 GMT

The code to convert the flat file to XML is primarily inside the FlatfileParser created earlier. Use the Python CGI API to grab the flat file from the query string Parse query string for flat file flatfile query.getvalue flatfile, 0 failure Conversion request not found or incorrectly formatted. print instatiate flat file parser amp display file ffp FlatfileParser print lt h1 gt Flat File lt h1 gt print lt p gt Flat file received lt p gt print lt p gt lt pre gt flatfile lt pre gt lt p gt After...

SMS Search MobilePython

Fri, 11 May 2012 08:42:35 GMT

Example 15 is a useful script a search tool for your SMS inbox. First the script asks for some text for which to search. Then it goes through your SMS inbox and shows excerpts of messages which contain the given string. You can see the full message by selecting a desired list item. query appuifw.query uSearch for , text index appuifw.selection_list hits, 1 First, the string for which to search is stored in the variable query. As in the previous example, we use the sms_messages function of the...

A custom model wxPython

Fri, 11 May 2012 08:22:35 GMT

The basic idea behind creating your model objects is simple. Construct your data classes without worrying about how they will be displayed. Then document a public interface for that class which will be accessible to the display objects. Obviously, the size and complexity of the project will determine how formal this public declaration needs to be. In a small project, with simple objects, it's probably enough to do the simple thing and allow the View objects direct access to the attributes of...

Note If you create a scale matrix with a negative scale value it will have the effect of flipping everything so that left becomes right top becomes bottom and front becomes back Pygame Game Development

Fri, 11 May 2012 04:00:54 GMT

You can also create a scale matrix with three different values for each axis, which scales the object differently in each direction. For example, Matrix44.scale 2.0, 0.5, 3.0 will create a matrix that makes an object twice as wide, half as tall, and three times as deep You are unlikely to need this very often, but it can be useful. For example, to simulate a plume of dust from a car tire, you could scale a model of a cloud of dust unevenly so that it looks like the tires are kicking it up. To...

PROBLEM SET Enz Engineering with Python

Thu, 10 May 2012 20:52:23 GMT

note that B is obtained by interchanging the first two rows of A . Knowing that determine B-1. 2. Invert the triangular matrices 6. Invert the following matrices with any method 7. Invert the matrix by any method and comment on the reliability of the result. 8. The joint displacements u of the plane truss in Problem 14, Problem Set 2.2, are related to the applied joint forces p by is called the stiffness matrix of the truss. If Eq. a is inverted by multiplying each side by K-1, we obtain u K-1...

FlowLayout Jython

Thu, 10 May 2012 20:27:48 GMT

TheFlowLayout class is the simplest of the layout managers. Actually, it's the second simplest I'll explain later. As components ne added one at o time to the conthiper, they're dosittolied from lgft to right and from top to bottom. When one row fills us, the components Pegin filling up the next row. You car set the hligssment of each row so that the components car de centered or lefs- oh rigri-alignod. Here's an interactive FlowLayo ut example. Import the FlowLayo ut class ard some container...

Vector Addition Pygame Game Development

Thu, 10 May 2012 18:55:12 GMT

Vector addition combines two vectors to produce a single vector that has the combined effect of both. Let's say soldier Alpha has to rendezvous with a drop ship at point C 15, 45 after picking up whatever the droid at point B was guarding. The vector from B to C is -15, 10 , which means he has to go back 15 units in the x direction and continue on 5 units in the y direction. If we add the components of the BC vector to the AB vector, we get a vector that would take us from A to C see Figure 5-3...

Info Tcz PythonTutorial

Thu, 10 May 2012 14:52:59 GMT

pay rate as arguments. The gross pay is displayed. def calc_pay_with_QT hours, rate Calculate the number of overtime hours worked. overti_me_hours hours - BAS __H0URS Calculate the amount of overtime pay. overtime_pay overtime__hours rate OT_MULTIPLIER gross pay BASE_HQURS rate overtime_pay Display the gross pay. print 'The gross pay is .2f.' The calc_regular_pay function calculates pay with no overtime. It accepts the hours worked and the hourly pay rate as arguments. The gross pay is...

How can I manage the size of grid elements wxPython

Thu, 10 May 2012 10:17:45 GMT

The grid control offers several different methods to manage the size of cells, rows, and columns. In this section we'll discuss each of these methods. Figure 14.4 displays some of the ways to change the size of a specific cell. Listing 14.5 displays the code for creating a grid with resized cells, rows, and columns. Figure 14.4 A sample grid, showing resized cells, rows, and columns Listing 14.5 Code sample for resized cells wx.Frame._init_ self, None, title Grid Sizes, size 600,300 grid...

Semantic Similarity Python Language Processing

Thu, 10 May 2012 01:55:41 GMT

We have seen that synsets are linked by a complex network of lexical relations. Given a particular synset, we can traverse the WordNet network to find synsets with related meanings. Knowing which words are semantically related is useful for indexing a collection of texts, so that a search for a general term such as vehicle will match documents containing specific terms such as limousine. Recall that each synset has one or more hypernym paths that link it to a root hypernym such as entity.n.01....

Setting label sizes wxPython

Wed, 09 May 2012 19:08:11 GMT

The label area on the grid has a separate set of sizing functions. In this case, you are setting the width of the row labels, and the height of the column labels, which means you are treating the column labels as a special row, and the row labels as a special column. As an example, look at a spreadsheet and notice how the row and column labels are laid out. The setter methods are SetRowLabelSize width , which sets the width of the row labels, and SetColLabelSize height , which sets the width of...

Business Process and Modeling Python XML Processing

Wed, 09 May 2012 08:54:07 GMT

In ebXML, business process and information modeling is not mandatory. But if it is used, it is required to be UMM UN CEFACT Modeling Methodology . This is a modeling language that uses UML Universal Modeling Language , which is commonly used in object-oriented programming design. The UMM approach separates operational and functional views and relies on two view constructs the Business Operational View BOV and the Functional Service View FSV . The operational view covers such things as the...

Handling Errors IronPythonDevelopment

Wed, 09 May 2012 00:17:06 GMT

So far, our application has been simple enough that we haven't encountered much in the way of errors. Even before we put RequiredFieldValidators on the page, the lack of any user input still didn't really disrupt the flow of the application. We can artificially induce an error and see what the user would see, and this alone should prove sufficient evidence of the need for judicious error handling and reporting. Open thankYou.aspx.py and modify it to look like Listing 8-25. Listing 8-25....

Creating the CGI Script Python XML Processing

Wed, 09 May 2012 00:14:30 GMT

The xslt.cgi script pulls the stylesheets together and coordinates the processing and updating of the XML on disk. While this application lets you edit and display XML in your browser, it only consists of a single CGI script and two XSL sheets. The source data that may constantly change is also stored on disk as XML. XSLT transformations can be done programmatically using the xml.xslt.processor.Processor class provided 4XSLT is installed, as shown earlier . When the CGI script launches, it...

bigdigitspy Python Programming Techniques

Tue, 08 May 2012 22:43:44 GMT

The first program we will review is quite short, although it has some subtle aspects, including a list of lists. Here is what it does Given a number on the command line, the program outputs the same number onto the console using big digits. At sites where lots of users share a high-speed line printer, it used to be common practice for each user's print job to be preceded by a cover page that showed their username and some other identifying details printed using this kind of technique. We will...

MSXML Node Object Python XML Processing

Tue, 08 May 2012 21:34:23 GMT

The Node object is the fundamental object of the DOM and of MSXML3.0. This interface supports the common methods used throughout this book when working with the DOM. Appends the supplied node to child NodeList for this element. cloneNode Creates a new node that is a complete copy of this particular node. Returns true if the node has children. insertBefore newChild, referenceChild Takes the node supplied as newChild and inserts it in this node's NodeList immediately prior to the supplied...

Method Calls Python Object Oriented Programming

Tue, 08 May 2012 20:43:42 GMT

gt gt gt set dir b'abc' - set dir 'abc' As you can see, str and bytes have almost identical functionality. Their unique attributes are generally methods that don't apply to the other for instance, decode translates a raw bytes into its str representation, and encode translates a string into its raw bytes representation. Most of the methods are the same, though bytes methods require bytes arguments again, 3.0 string types don't mix . Also recall that bytes objects are immutable, just like str...

What is a grid sizer wxPython

Tue, 08 May 2012 20:11:09 GMT

The simplest sizer offered by wxPython is the grid. As the name implies, a grid sizer places its children in a two-dimensional grid. The first widget in the sizer's child list goes in the upper left corner of the grid, and the rest are laid out left-to-right and top-to-bottom, until the last widget is placed in the bottom right of the grid. Figure 11.1 shows an example, with nine widgets placed in a 3 x 3 grid. Notice that there is a slight gap between each widget. When you resize the grid...

Rapid GUI Programming with Python and Qt 1 PyQtProgramming

Tue, 08 May 2012 19:06:28 GMT

The Definitive Guide to PyQt Programming Upper Saddle River, NJ Boston Indianapolis San Francisco New York Toronto Montreal London Munich Paris Madrid HALL Capetown Sydney Tokyo Singapore Mexico City Many of the designations used by manufacturers and sellers to distinguish their products are claimed as trademarks. Where those designations appear in this book, and the publisher was aware of a trademark claim, the designations have been printed with initial capital letters or in all capitals. The...

Caching Tool CherryPyGuide

Tue, 08 May 2012 10:15:03 GMT

Purpose The purpose of this tool is to provide basic in-memory caching of CherryPy generated content. POST, PUT, DELETE Tuples of strings of HTTP methods not to be cached. These methods will also invalidate delete any cached copy of the resource. Class object to be used for caching. A comprehensive example would be out of the scope of this book but if you are interested in this tool you should first look at the CherryPy test suite as well as visit the CherryPy users' mailing-list.

Library CherryPyGuide

Tue, 08 May 2012 09:55:32 GMT

CherryPy comes with a set of modules covering common tasks when building a web application such as session management, static resource service, encoding handling, or basic caching. CherryPy is a long-running Python process, meaning that if we modify a Python module of the application, it will not be propagated in the existing process. Since stopping and restarting the server manually can be a tedious task, the CherryPy team has included an autoreload module that restarts the process as soon as...

Info Dlv PythonTutorial

Tue, 08 May 2012 07:02:17 GMT

print 'The retail price is .2f.' retail Calculate the retail price, retail wholesale MARK UP Program Output with input shown in bold Enter the item's wholesale cost Enter ERROR the cost cannot be negative. Enter the correri. wnnlfiSaIh cost O.SO Enter The retail price is 1.25. o you have another item Enter y for yes E ter

Listing Interacting with DOM elements from inside Silverlight IronPythonIntroduction

Tue, 08 May 2012 04:22:28 GMT

from System.Windows.Browser import HtmlPage document HtmlPage.Document element document.some_element element.innerHTML Some lt em gt HTML lt em gt . element2 element2.SetStyleAttribute 'border', 'solid black 2px' element3 document.GetElementById 'some_textbox' element3.SetProperty 'disabled', True element3.value 'Text in a textblock' As well as using innerHTML we could also use innerText. Because we have access to these attributes, we can use all our favorite AJAX tricks from Silverlight. Some...

List of Exercises Python Scientific Programming

Mon, 07 May 2012 20:30:18 GMT

Exercise 1.1 Compute Exercise 1.2 Write a Hello, World Exercise 1.3 Convert from meters to British length units 43 Exercise 1.4 Compute the mass of various substances 43 Exercise 1.5 Compute the growth of money in a bank 43 Exercise 1.6 Find error s in a Exercise 1.7 Type in program text Exercise 1.8 Type in programs and debug them 44 Exercise 1.9 Evaluate a Gaussian Exercise 1.10 Compute the air resistance on a football 45 Exercise 1.11 Define objects in IPython Exercise 1.12 How to cook the...

Accessing the registry with winreg PythonComponents

Mon, 07 May 2012 17:31:39 GMT

The standard library _winreg also exposes the Windows registry API. Since the underlying API is the same, the functions in _winreg are very similar to the registry API in win32api. Table 37-3 shows the correspondence Table 37-3 winreg and win32api Functions

Lambda Functions Python Programming Techniques

Mon, 07 May 2012 07:36:57 GMT

Lambda functions are functions created using the following syntax The parameters are optional, and if supplied they are normally just comma-separated variable names, that is, positional arguments, although the complete argument syntax supported by def statements can be used. The expression cannot contain branches or loops although conditional expressions are allowed , and cannot have a return or yield statement. The result of a lambda expres- Genera-sion is an anonymous function. When a lambda...

Nevilles Method Engineering with Python

Sun, 06 May 2012 12:21:25 GMT

Newton's method of interpolation involves two steps computation of the coefficients, followed by evaluation of the polynomial. This works well if the interpolation is carried out repeatedly at different values of x using the same polynomial. If only one point is to be interpolated, a method that computes the interpolant in a single step, such as Neville's algorithm, is a better choice. Let Pk x, xi 1, , xi k denote the polynomial of degree k that passes through the k 1 data points x,, yi , xi...

Part The Sky at Night PythonVisualization

Sun, 06 May 2012 04:29:32 GMT

To create a simulated image of the night sky, we use the script in Listing 9-10. Listing 9-10. Creating an Image ofthe Sky at Night, nightsky.py create a fictitious night sky from random import randrange as rr parameters for the simulated night sky image img_size 800 star parameters number of pointy edges and radius min_num_points 5 max_num_points 11 min_star_radius 2 max_star_radius 10 star parameter 'thinness' is on a scale of 1 to 10 min_thin 5 draw the night sky figure facecolor 'k'...

Introduction Dng PythonXML

Sat, 05 May 2012 17:53:19 GMT

This chapter introduces Python's data-handling capabilities that use data structures. Data structures hold and organize information data . Many types of data structures exist, and each type has features appropriate for certain tasks. Sequences, often called arrays in other languages, are data structures that store usually related data items. Python supports three basic sequence data types the string, the list and the tuple. Mappings, often called associative arrays or hashes in other languages,...

Regular Expressions PythonVisualization

Sat, 05 May 2012 16:02:54 GMT

Regular expressions are pattern-matching expressions used for searching and replacing text. At times, they are more flexible than the string operations presented previously. To use regular expressions, you'll have to import the regular expression module named re , which is part of the standard library. The module re is similar to Perl's built-in support of regular expressions. Your next step is to design a pattern to match against and decide what function to use on that pattern. The most...

Regular Expression Patterns PythonVisualization

Sat, 05 May 2012 16:02:07 GMT

A regular expression pattern is basically a string. The pattern can contain both regular characters and special characters. A regular character matches itself. So the pattern 'a' matches the character 'a' whenever encountered, and the pattern 'txt' matches the string 'txt' whenever encountered gt gt gt re.split r'a', 'Flatland' F1-, 'tl', 'nd' gt gt gt re.split r'txt', '97.txt' '97.', So far, re.split is similar to the split function introduced previously in the chapter. However, the strength...

Examining Tracebacks PythonComponents

Fri, 04 May 2012 21:09:43 GMT

If your program throws an uncaught exception, it exits, and the Python interpreter prints a traceback, or stack trace. However, your program need not crash to use traceback objects the traceback module provides a suite of functions to work with them. One usually grabs a traceback with a call to sys.exc_info , which returns a tuple of the form Exception,Exception, Traceback . In an interactive session, meeting an unhandled exception populates the values sys.last_type, sys.last_value, and...

Extracting GPS Data PythonVisualization

Fri, 04 May 2012 13:45:54 GMT

In the case of a GPGSV header, the number of satellites is the fourth entry. In case of a GPRMC header, we have a bit more interesting information. The second field is the timestamp, the fourth field is the latitude, the sixth field is the longitude, and the eighth field is the velocity. Again, turn to the NMEA 0183 format for more details. Table 1-1 summarizes the fields and their values in a GPRMC line. Table 1-1. GPRMC Information Excerpt Table 1-1. GPRMC Information Excerpt Some caveats...

Chapter Tov BeginningPython

Fri, 04 May 2012 12:14:36 GMT

Each of the following exercises builds on the exercises that preceded it 1. Add an option to the Omelet class's mix method to turn off the creation messages by adding a parameter that defaults to True, indicating that the mixing . . . messages should be printed. 2. Create a method in class Omelet that uses the new mix method from Exercise 1. Called quick_cook, it should take three parameters the kind of omelet, the quantity wanted, and the Fridge that they'll come from. The quick_cook method...

Example The BikeStock Modules Classes Python Programming Techniques

Fri, 04 May 2012 06:42:34 GMT

The BikeStock module uses a BinaryRecordFile.BinaryRecordFile to provide a simple stock control class. The stock items are bicycles, each represented by a BikeStock.Bike instance, and the entire stock of bikes is held in a Bike-Stock.BikeStock instance. The BikeStock.BikeStock class aggregates a dictionary whose keys are bike IDs and whose values are record index positions, into a BinaryRecordFile.BinaryRecordFile. Here is a brief example of use to get a feel for how these classes work bicycles...

Creating Web Servers Python Programming Basics

Thu, 03 May 2012 11:02:10 GMT

You already know that CGI request processing involves Web servers and clients. Usually, we use browsers, such as Netscape Navigator and Internet Explorer, as Web clients. The most popular Web servers are IIS, Apache, and Netscape. You can use Python for creating a Web server and Web clients. Some of the modules available in Python for building Web servers are SocketServer, BaseHTTPServer, SimpleHTTPServer, and CGIHTTPServer. The SocketServer module is used for creating general IP servers. It...

newtonPoly Engineering with Python

Thu, 03 May 2012 03:51:34 GMT

This module contains the two functions required for interpolation by Newton's method. Given the data point arrays xData and yData, the function coeffts returns the coefficient array a. After the coefficients are found, the interpolant Pn x can be evaluated at any value of x with the function evalPoly. Evaluates Newton's polynomial p at x. The coefficient vector a can be computed by the function 'coeffts'. Computes the coefficients of Newton's polynomial. n len xData - 1 Degree of polynomial p a...

How can I display the page title in a frames title bar wxPython

Thu, 03 May 2012 01:55:42 GMT

One thing you've probably noticed in your web browser is that the display window is not the only element of the browser. Among the other elements of note are a title bar and status bar in the containing frame. Typically, the title bar displays the title of the HTML page being displayed, and the status bar displays information about links as they are moused over. In wxPython, there are a couple of shortcuts that allow you to set this relationship up quickly and easily. Figure 16.3 displays this...

Description Sxc PythonReference

Thu, 03 May 2012 00:40:55 GMT

An alternative character used by the OS to separate pathname components, or None if only one separator character exists. This is set to ' ' on DOS and Windows systems, where sep is a backslash. The string used to refer to the current working directory '.' for UNIX and Windows and ' ' for the Macintosh. The path of the null device for example, dev null . Character that separates the base filename from its type for example, the '.' in 'foo.txt' . The string used to refer to the parent directory '...

Modules reload Jython

Wed, 02 May 2012 23:39:50 GMT

Thereload fufctiof allows you to dynamically reload e module. It comes in very handy when you're debugging code. Here's an example with the string module gt reload string lt module ' string' gt During development of a module, it's often necessary to moke minor changes. Instead of exiting the interactive interpreter, you can moke your changes and then reload. reload seeds e reference to the module. Let's sty you're using the from lt module gt import lt obj ect gt form of the import statement. In...

Extending Types by Subclassing Python Object Oriented Programming

Wed, 02 May 2012 19:38:46 GMT

Beginning with Python 2.2, all the built-in types in the language can now be subclassed directly. Type-conversion functions such as list, str, dict, and tuple have become built-in type names although transparent to your script, a type-conversion call e.g., list 'spam' is now really an invocation of a type's object constructor. This change allows you to customize or extend the behavior of built-in types with user-defined class statements simply subclass the new type names to customize them....

Using the Skip method wxPython

Tue, 01 May 2012 22:17:07 GMT

The first handler function found for an event halts processing on that event unless the Skip method of the event is called before the handler returns. Calling Skip allows additional handler bindings to be searched for, following the rules described in step 4 of 3.4.1, so parent classes and parent windows are searched just as if the first handler didn't exist. In some cases, you want the event to continue processing to allow the default behavior in the native widget to be executed along with...

Figure PyForm displaying a shelf of Actor objects ProgrammingPython

Tue, 01 May 2012 13:22:18 GMT

PyForm uses a three-window interface to the table being browsed all windows are packed for proper window expansion and clipping, as set by the rules we studied earlier in this book. The window in the upper left of Figure 16-1 is the main window, created when PyForm starts it has buttons for navigating through a table, finding items by key, and updating, creating, and deleting records more useful when browsing tables that persist between runs . The table dictionary key of the record currently...

Info Tcl PythonTutorial

Sun, 29 Apr 2012 13:19:11 GMT

51 Enter the Tkinter main loop. 54 Create an instance of the MyGUI class. Figure 12-8 Window displayed Program 12-6 Figure 12-8 Window displayed Program 12-6 Take a closer loolc at lines 12 and 13 self-top - frame Tkinter. Frame self .main_window self, bo 11 om_f r ame Tkinter. Frame self -main window These, lines create two Frame objects. The self . main window argument that appears inside the parentheses cause the Frames to be added to the mainjwindow widget. Lines 17 through 22 create three...

super Pitfalls Python Designing and Coding

Sun, 29 Apr 2012 07:27:18 GMT

Back to super. Its usage, when using multiple inheritance hierarchy, can be quite dangerous mainly because of initialization of classes. In Python, the base classes are not implicitly called in_init_, and so it is up to the developer to call them. Here In the following example taken from James Knight's website http fuhm.net super-harmful , a c class that calls its base classes using the_init_method will gt gt gt print MRO , x._name_ for x in C._mro_ MRO 'C', 'A', 'B', 'object' gt gt gt C C A B...

MainWindowStyle Programs Python Programming Techniques

Fri, 27 Apr 2012 03:16:15 GMT

Although dialog-style programs are often sufficient for simple tasks, as the range of functionality a program offers grows it often makes sense to create a complete main-window-style application with menus and toolbars. Such applications are usually easier to extend than dialog-style programs since we can add extra menus or menu options and toolbar buttons without affecting the main window's layout. In this section we will review the bookmarks-tk.pyw program shown in Figure 15.4. The program...

Info Cge Python Language Overview

Wed, 25 Apr 2012 20:10:01 GMT

Unlike many things in the programming world, a zero when running a program indicates a successful status, meaning the file was copied. We talked about the files and directories portion of the os module back in Chapter 6, so there is no real reason to rehash it here. Instead, you should spend your time looking through the various components of the modules, to see what you will need when you are writing your own applications in Python. By the way, the win32api modules are all available free of...

Configuring the Label the Color structure IronPythonIntroduction

Wed, 25 Apr 2012 19:32:01 GMT

Our form, with a single label, is still going to look pretty dull. In this section, you'll add some color, literally. All controls have two properties particularly related to color, ForeColor and Back-Color. BackColor sets the background color of the control. The ForeColor affects elements of the control, such as the text of a label. You specify the color using the Color structure from the System.Drawing namespace. System.Drawing lives in its own assembly to use it, you need to add a reference...

Info Thh IronPythonTutorial

Wed, 25 Apr 2012 17:42:41 GMT

FIGURE 14-6 The output shows the process used to work with dynamic objects. FIGURE 14-6 The output shows the process used to work with dynamic objects. The point of all this is that you can implement a kind of dynamic object strategy for static languages, but it's cumbersome compared to IronPython. You might use this approach when you need to provide a dynamic strategy for something small within C or Visual Basic. This technique is also useful for understanding how IronPython works, at a very...

Try it out Evx PythonProgramming

Wed, 25 Apr 2012 16:13:13 GMT

1 Write a program that asks for a person's name, age, and favorite color, and then prints it out in one sentence. A run of the program should look like this gt gt gt RESTART Your name is Sam you are 12 years old and you like green 2 Remember our times-table program from chapter 8 listing 8.5 Write an improved version that uses tabs to make sure everything lines up nicely in columns. 3 Write a program that calculates all the fractions of 8 for example, 1 8, 2 8, 3 8, . . . up to 8 8 and displays...

Extended Sequence Unpacking in Python Python Object Oriented Programming

Wed, 25 Apr 2012 15:49:08 GMT

The prior section demonstrated how to use manual slicing to make sequence assignments more general. In Python 3.0 but not 2.6 , sequence assignment has been generalized to make this easier. In short, a single starred name, X, can be used in the assignment target in order to specify a more general matching against the sequence the starred name is assigned a list, which collects all items in the sequence not assigned to other names. This is especially handy for common coding patterns such as...

Polymorphism Dynamic Binding and Duck Typing PythonReference

Wed, 25 Apr 2012 14:49:24 GMT

Dynamic binding also sometimes referred to as polymorphism when used in the context of inheritance is the capability to use an instance without regard for its type. It is handled entirely through the attribute lookup process described for inheritance in the preceding section.Whenever an attribute is accessed as obj . attr, attr is located by searching within the instance itself, the instance's class definition, and then base classes, in that order. The first match found is returned. A critical...

What styles control the display of the tree control wxPython

Wed, 25 Apr 2012 14:45:33 GMT

The display styles for the tree control fall into four basic categories. The first set defines whether the tree control has explicit buttons displayed next to the text of a parent object as a target for expanding or collapsing the parent node. These are displayed in table 15.1. Table 15.1 Button codes for the tree control Table 15.1 Button codes for the tree control The tree control has whatever buttons are typical for the platform. For example on MS-Windows a small button is used to indicate...

A CronLike Scheduler Python System Administration

Wed, 25 Apr 2012 14:12:00 GMT

Let's go back to the ticket scheduler implementation. As you remember, the scheduling information is stored in the probingschedule table, which has the following fields Table 9-10. The probing schedule table fields Table 9-10. The probing schedule table fields Points to the corresponding host probe entry. This field contains the ID of the host probe row. My implementation of the scheduler is slightly different from the logic that the cron application is using. The cron configuration allows you...

UnitTest JythonGuide

Wed, 25 Apr 2012 12:33:48 GMT

First we will take a look at the most classic test tool available in Python UnitTest. It follows the conventions of most xUnit incarnations such as JUnit you subclass from TestCase class, write test methods which must have a name starting with test , and optionally override the methods setUp and tearDown , which are executed around the test methods. And you can use the multiple assert methods provided by TestCase. The following is a very simple test case for functions of the built-in math...

BoxLayout Jython

Wed, 25 Apr 2012 12:14:29 GMT

You may remember that I referred to FlowLayo ut as the second simplest Iooou manager. It used to be the easiest, but that was before BoxLayout, which was added as part of JFC Swirg. BoxLayout car be used with AWT components, but it wo rks better with the JFC variety. BoxLayout has otIo one parameter, AXIS, and there are opty two choices X and Y. Here's o short interactive example. ImportBoxLayout, JFrame, and JButton from javax.swing. gt gt gt from javax.swing import BoxLayout, JFrame, JButton...

Attribute Name Qualification Python Object Oriented Programming

Wed, 25 Apr 2012 08:42:09 GMT

Now that you're becoming more familiar with modules, we should look at the notion of name qualification fetching attributes in more depth. In Python, you can access the attributes of any object that has attributes using the qualification syntax object. attribute. Qualification is really an expression that returns the value assigned to an attribute name associated with an object. For example, the expression module2.sys in the previous example fetches the value assigned to sys in module2....

Glade a GUI Builder for pyGTK PythonLearning

Wed, 25 Apr 2012 07:13:29 GMT

The great thing about pyGTK is that you almost never have to write the GUI by hand. That's what Glade is for. Glade is a GUI construction kit It provides a GUI you can use to design your own GUI. Once you're done, it writes a description of a GUI layout to an XML file see Chapter 15 for more information about XML . A library called libglade can then read that XML file and render the corresponding GUI. Instead of instantiating a bunch of Python objects and calling show on all of them, you just...

How do I create a list control wxPython

Wed, 25 Apr 2012 03:47:06 GMT

A wxPython list control is an instance of the class wx.ListCtrl. The constructor is similar to the other widget constructors, as shown here wx.ListCtrl parent, id, pos wx.DefaultPosition, size wx.DefaultSize, style wx.LC_ICON, validator wx.DefaultValidator, name listCtrl These parameters contain values from other widget constructors we have seen. The parent is the containing widget, the id is the wxPython identifier, with -1 indicating automatic creation. Explicit layout is managed by pos and...

The Message widget TkinterReference

Wed, 25 Apr 2012 01:54:01 GMT

This widget is similar to the Label widget see Section 11, The Label widget p. 44 , but it is intended for displaying messages over multiple lines. All the text will be displayed in the same font if you need to display text with more than one font, see Section 23, The Text widget p. 78 . To create a new Message widget as the child of a root window or frame named parent This constructor returns the new Message widget. Options may be any of these This constructor returns the new Message widget....

Pump up the volume PythonProgramming

Tue, 24 Apr 2012 23:26:25 GMT

To make the program more useful, the DJ wants to be able to dynamically and interactively control the volume of the track as it plays. Basically, as the track plays, the DJ wants to fiddle with the volume. To make the program more useful, the DJ wants to be able to dynamically and interactively control the volume of the track as it plays. Basically, as the track plays, the DJ wants to fiddle with the volume. In the physical world, most devices that have a volume control provide either a large,...

Editing a pickle File Jython

Tue, 24 Apr 2012 23:06:27 GMT

At this point you may be wondering what the file created with the pickle module looks like. It's just a text file. In fact, we can edit it to change its valuas. Here's the original file With your favorite text editor, change 'Tony Scalise'to 'Kelly Pagleochini' or any name you like , and change the phone number from '555-555-3699'to '555-555-2577'. Now, in an interactive session, we'll show how this changes the object instance. First close the file and reopen it. gt gt gt address_file.close...

Handling multiple bindings Python Tkinter Programming

Tue, 24 Apr 2012 22:56:09 GMT

As I mentioned in the note above, you can bind events at each of the four binding events. However, because events are propagated, that might not result in the behavior that you intended. For a simple example, suppose you want to override the behavior of a widget, and rather than have BACKSPACE remove the previous character, you want to insert h into the widget. So you set up the binding like this text.bind ' lt BackSpace gt ', lambda e dobackspace e and define the callback like this def...