1 ITT751 Advance Internet and Web Programming - PYTHON Presented by: Saidatul Nurah, Sazimah and...

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ITT751 Advance Internet and Web Programming -

PYTHON

Presented by:

Saidatul Nurah, Sazimah and Noor Ilyani

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Introduction to Python Python is a dynamic object-oriented programming language that can

be used for many kinds of software development. It offers strong support for integration with other languages and tools, comes with extensive standard libraries. Many Python programmers report substantial productivity gains and feel the language encourages the development of higher quality, more maintainable code.

Python runs on Windows, Linux/Unix, Mac OS X, OS/2, Amiga, Palm Handhelds, and Nokia mobile phones. Python has also been ported to the Java and .NET virtual machines

Python is distributed under an OSI-approved open source license that makes it free to use, even for commercial products

The Python Software Foundation (PSF) holds and protects the intellectual property rights behind Python, underwrites the PyCon conference, and funds grants and other projects in the Python community

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About Python Python is a remarkably powerful dynamic programming language

that is used in a wide variety of application domains. Python is often compared to Tcl, Perl, Ruby, Scheme or Java Some of its key distinguishing features include:

very clear, readable syntax strong introspection capabilities intuitive object orientation natural expression of procedural code full modularity, supporting hierarchical packages exception-based error handling very high level dynamic data types extensive standard libraries and third party modules for

virtually every task extensions and modules easily written in C, C++ (or Java for

Jython, or .NET languages for IronPython) embeddable within applications as a scripting interface

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About Python (Cont.)

Python is powerful and fast Python use the phrase “batteries included” to describe

the standard library, which covers everything from processing to zip files.

The language itself is a flexible powerhouse that can handle practically any problem domain.

Build flexible data-driven code using Python's powerful and dynamic introspection capabilities and advanced language features.

Can build our own web server and lets you write the code that you need.

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Python plays well with others Python can integrate with COM, .NET, and CORBA

objects. Example:- For Java libraries, use Jython, an implementation of

Python for the Java Virtual Machine. For .NET, try Iron Python , Microsoft's new implementation

of Python for .NET, or Python for .NET Python is also supported for the Internet

Communications Engine (ICE) and many other integration technologies

If you find something that Python cannot do or you need the performance advantage of low-level code, you can write extension modules in C or C++ or even wrap existing code with SWIG or Boost Python. Wrapped modules appear into the program exactly like native Python code.

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Python runs everywhere Python is available for all major operating

systems: Windows, Linux/Unix, OS/2, Mac, Amiga, among others.

There are even versions that run on .NET, the Java virtual machine, and Nokia Series 60 cell phones.

The same source code will run unchanged across all implementations.

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Python is friendly and easy to learn The Python newsgroup is known as one of the

friendliest around. The avid developer and user community

maintains a wiki, hosts international and local conferences, runs development sprints, and contributes to online code repositories.

Python also comes with complete documentation, both integrated into the language and as separate web pages.

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Python is open The Python implementation is under an open

source license that makes it freely usable and distributable, even for commercial use.

The Python license is administered by the Python Software Foundation.

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History of Python

Python was first created by Guido von Rossum in 1990 and was named after the Brit-com Monty Python's Flying Circus. It has since been developed by a large team of volunteers and is freely available from the Python Software Foundation. The most recent version of Python, 2.5.1, was released on 18 April, 2007.

Python is now found in many incarnations. At the website of the Python Software Foundation, Python is written in C. Other incarnations exist. A Java-based version of Python exists in Jython and may be used to work with Java code natively. Iron Python, a C# version, exists for the .Net and Mono platforms and allows C# programmers access to Python's power and flexibility.

In each of these instances, Python is written in one language and works natively with that language; however, it also interacts very well with other languages through its many modules.

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Getting Started – How to Install?

Installing Python is generally easy, and nowadays many Linux and UNIX distributions include a recent Python. Even some Windows computers (notably those from HP) now come with Python already installed.

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Getting Started – How to Install? (Cont.)

Downloading Python Before you start, you will need Python on your computer, but you

may not need to download it. First of all check (by entering python in a command line window) that you don't already have Python installed!

If you see a response from a Python interpreter it will include a version number in its initial display. Generally any recent version will do, as Python makes every attempt to maintain backwards compatibility.

If you need to install, you may as well download the most recent stable version. This is the one with the highest number that isn't marked as an alpha or beta release. Currently the stable version is Python 2.5.1.

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Getting Started – How to Install? (Cont.)

If you're running Windows: the most stable Windows download is Python 2.5.1 for Windows.

If you are using a Mac, MacOS 10.2 (Jaguar), 10.3 (Panther) and 10.4 (Tiger) come with Python already, but you will probably want to install the latest universal build. For MacOS X 10.3 and later: install python-2.5.1-macosx.dmg. This is a Universal installer. The Universal OS X image contains an installer for python 2.5.1 that works on Mac OS X 10.3.9 and later, on both PPC and Intel Macs.

For Red Hat, install the python2 and python2-devel packages.

For Debian or Ubuntu, install the python2.5 and python2.5-dev packages.

For Gentoo, install the '=python-2.5*' ebuild (you may have to unmask it first).

For Linux, most Linux distributions have Python installed.

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Python Features

Beginners Guide / overview Python is a clear and powerful object-oriented

programming language, comparable to Perl, Ruby, Scheme, or Java.

Python's notable features: Uses an elegant syntax, making the programs you

write easier to read. Is an easy-to-use language that makes it simple to

get your program working. This makes Python ideal for prototype development and other ad-hoc programming tasks, without compromising maintainability

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Python Features (Cont.) Comes with a large standard library that supports many common

programming tasks such as connecting to web servers, searching text with regular expressions, reading and modifying files.

Python's interactive mode makes it easy to test short snippets of code. There's also a bundled development environment called IDLE.

Is easily extended by adding new modules implemented in a compiled language such as C or C++.

Can also be embedded into an application to provide a programmable interface.

Runs on many different computers and operating systems: Windows, MacOS, many brands of Unix, OS/2.

Is free software in both senses. It doesn't cost anything to download or use Python, or to include it in your application. Python can also be freely modified and re-distributed, because while the language is copyrighted it's available under an open source license.

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Python Features (Cont.) programming-language features of Python are:

A variety of basic data types are available: numbers (floating point, complex, and unlimited-length long integers), strings (both ASCII and Unicode), lists, and dictionaries.

Python supports object-oriented programming with classes and multiple inheritances.

Code can be grouped into modules and packages.

The language supports raising and catching exceptions, resulting in cleaner error handling.

Data types are strongly and dynamically typed. Mixing incompatible types (e.g. attempting to add a string and a number) causes an exception to be raised, so errors are caught sooner.

Python contains advanced programming features such as generators and list comprehensions.

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Python Features (Cont.)

Python contains advanced programming features such as generators and list comprehensions.

Python's automatic memory management frees you from having to manually allocate and free memory in your code.

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The Architecture of Python

Python is a portable, interpreted, interactive, and object-oriented programming language. It is widely used for all kinds of Internet applications ranging from CGI scripts to complex servers, including Zope, a very popular, open source web server. As it is being developed and maintained with an Open Source development model, the source code is meant to be self-documenting.

i. Python - The Language ii. Python – Architecture Business Cycle iii. Python – Architectural Structures iv. Python - Styles

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The Architecture of Python (Cont.)

Python - The Language

Python is very expressive and easy to use. It's also considerably more readable than PERL. One of the best things about Python is that it allows users to define classes and create objects.

According to Mark Lutz in Learning Python lists the following features and benefits of Python: Example:-

Features Benefits

No compile or link steps Rapid development cycle turnaround

No type declarations Simpler, shorter, and more flexible programs

Object-oriented programming

Code reuse, C++, Java, and COM integration

Simple, clear syntax and design

Readability, maintainability, ease of learning

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Python - Architecture Business Cycle

In Python's architecture business cycle (ABC), the influences on the architect have evolved over time, with the biggest change occurring when the source code was released to the public making Python open source.

The illustration below shows the various factors involved in the Python ABC.

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Python's ABC. (Adapted from ABC diagrams in Software Architecture in Practice by Bass, et al., 98).

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Python - Architectural Structures

The term between Python, the language and Python, the interpreter are the interpreter is the system being implemented by a Python developer; the language is the system being executed or used by a Python programmer.

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Architecture Overview of Python

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File Layout

The following is a description of the physical file layout of Python. Python has four main folders as depicted in the diagram below.

Python uses the term module to mean extended functionality, but, by the Python convention, there is always only one file in a module.

1. The Module folder 2. The Parser folder 3. The Objects folder 4. The Lib folder

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The Architecture of Python (Cont.)iv. Python - Architectural Styles

Focus on these factors:-

Layers ■ The Memory Manager

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The C/Python InterfaceAn example of relaxed layering is in the C/Python interface. A C program can employ three techniques to access Python objects.

The first technique, which is the easiest and provides the highest level of control, is the use of the Very-High Level Layer (VHLL).

The second technique is the use of concrete or built-in objects. Each of these objects defines its own type-dependent interface.

The third technique is the use of abstract objects. Example: a C program

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Reflection

Python does not implement a pure reflective architectural pattern. Reflection is evidenced in a program that is able to change its structure or behavior at run-time.

■ Textbook Reflection

■ Python Reflection

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The Architecture of Python (Cont.) Batch Sequential

The main interpreter of Python uses a Data Flow Architecture. In the Python interpreter each component could be a standalone program. In Python these components are integrated to achieve better performance, but the underlying theme hasn't changed from batch-sequential. Each component completes its task prior to the next one starting and calls the next component with the results of its transformation on the data.

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Application DomainPython is used in many application domains. There are for:

Web and Internet Development Python offers a wide range of choices for web development:

Writing basic CGI (Computer Graphic Interface) scripts. Frameworks such as Django and TurboGears. High-end solutions such as Zope. Advanced content management systems such as Plone.

For custom web solutions and other internet-based applications: Extensive support for XML. E-mail processing. Processing RSS (Really Simple Syndication) feeds. RSS is a family of

web feed formats used to publish frequently updated content such as blog entries, news headlines or pod casts.

Support for many other Internet protocols.

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Application Domain (Cont.)

Database Access Custom and ODBC interfaces to MySQL, Oracle, MS SQL Server,

PostgreSQL, SybODBC, and others are available for free download. Standard Database API. Object databases such as ZODB and Durus.

Desktop GUIs The Tk GUI development library is included with most binary

distributions for Python. wxWidgets GTK+ Qt Microsoft Foundation Classes through the win32 extensions Delphi

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Application Domain (Cont.)Scientific and NumericPython is widely used in scientific and numeric computing:BioinformaticsPython course in BioinformaticsPhysics

EducationPython is a superb language for teaching programming, both at the introductory level and for more advanced courses.Education Special Interest Group is a good place to start.pyBiblio links to many different resources.The Software Carpentry Course, funded by the Python Software Foundation.

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Application Domain (Cont.)Network ProgrammingIn addition to the web and internet support described above, Python also provides support for lower level network programming:Easy-to-use socket interface.Twisted Python, a framework for asynchronous network programming.

Software DevelopmentPython is often used as a support language for software developers, for build control and management, testing, and in many other ways.SCons for build control.Buildbot and Apache Gump for automated continuous compilation and testing.Roundup or Trac for bug tracking and project management.Integrated Development Environments.

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Application Domain (Cont.)

Game and 3D GraphicsPython is widely used in commercial and hobby game development:

A partial list of games is on the Python Games Wiki page.

PyGame and PyKyra are two of the game frameworks available for Python.

List of 3D rendering libraries available for Python.

PyWeek is a semi-annual game programming contest.

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Advantages of PythonPython is open source

You can get it for free. Free is not the same as unsupported; in fact, the Python support community is populated by the best minds in software today. Commercial software vendors have yet to match the quality and speed of support offered in the Python community. The combination of being freely available and also meticulously supported confers a powerful competitive advantage.

Furthermore, the open source evolution happened for good reason; namely, to answer the pressing need for modular, pluggable, highly communicable software that allows organizations to create solutions that work. Proprietary technologies, with all due respect for commercial enterprises, simply did not solve the underlying problems that businesses face. Solving those problems requires a set of open standards to encourage software solutions to work well together in a complete system. Open source software is part of that solution.

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Advantages of Python (Cont.)

Python is portable. The core Python language runs on any platform: Unix, Windows,

Macintosh, Linux, Amiga, Be-OS, OS/2, VMS, QNX, even MS-DOS. You can, however, write platform-specific code if your application requires it. Python has platform-specific extensions (like COM support, for example) for specialized functionality.

Python is all about speed and productivity. This is where Python shines. You simply will not find a language that is

easier to write and read. Moreover, since developers do not need to spend time compiling or porting to various platforms, development happens in a fraction of the time.

Python’s speed means you can support your customers better, faster, cheaper.

It takes a literal fraction of the time it once did to make bug fixes and enhancements.

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Advantages of Python (Cont.)

Python communicates seamlessly with almost anything. If you need to tie in something written in another language,

you can do it easily. While Python is excellent for almost any programming task, you may find some special need that can be fulfilled in another language. You can avail yourself of all the advantages of Python programming, and still integrate special modules written in other tools. In fact, Python excels at tying disparate components together.

Python is object-oriented. It is enough to point out that Python is innately object-

oriented. Its class model supports advanced concepts such as polymorphism, operator overloading, and multiple inheritance.

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Disadvantages of Python Not terribly fast on computationally intensive operations.

Language processor cares at a syntactic level, how many spaces are in a tab.

There is a limitation to using Python as a client-side solution for your Web applications: Each client machine must have Python installed. That's probably the greatest disadvantage that Python has among the other Active Scripting languages because Internet Explorer provides core support for VBScript and JScript.

Other problems with using Python as a client-side scripting language include the fact that it is only supported in Internet Explorer, it only works on Windows, and it requires that the Python Active Scripting component be installed.

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Syntax and Semantics

Python was designed to be a highly readable language.

Python uses indentation/whitespace, rather than curly braces or keywords, to delimit statement blocks.

An increase in indentation comes after certain statements; a decrease in indentation signifies the end of the current block.

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Syntax and Semantics (Cont.)

Python's statements include: The if statement, which conditionally executes a block of

code, along with else and elif (a contraction of else-if). The while statement, which runs a block of code until a

condition is False. The for statement, which iterates over an iterable,

capturing each element to a local variable for use by the attached block.

The class statement, which executes a block of code and attaches its local namespace to a class, for use in object oriented programming.

The def statement, which defines a function.

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Syntax and Semantics (Cont.)

Python uses duck typing, also known as latent typing. Type constraints are not checked at compile time; rather, operations on an object may fail, signifying that the given object is not of a suitable type.

Python includes a number of built-in types used for a variety of purposes such as, str, unicode, list, tuple, int, float, complex, bool etc.

Python also allows programmers to define their own types. This is in the form of classes, most often used for an object-oriented style of programming. New instances of classes are constructed by calling the class (ie, like FooClass()), and the classes themselves are instances of class type (itself an instance of itself), allowing metaprogramming and reflection.

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Why Using Python?

Python is over 10 years old, and its development process is quite mature at this point .

C programmers will find that the C source code for the Python interpreter is clearly written and easy to dive into.

Programming in Python is much more pleasant than programming in C, because you get nicely formatted trace backs instead of nasty core dumps and protection faults.

Can be run on any platform (UNIX, Windows or MacOS).

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Quotes

"Python is fast enough for our site and allows us to produce maintainable features in record times, with a minimum of developers," said Cuong Do, Software Architect, YouTube.com.

"Python has been an important part of Google since the beginning, and remains so as the system grows and evolves. Today dozens of Google engineers use Python, and we're looking for more people with skills in this language." said Peter Norvig, director of search quality at Google, Inc.

"I have the students learn Python in our undergraduate and graduate Semantic Web courses. Why? Because basically there's nothing else with the flexibility and as many web libraries," said Prof. James A. Hendler. University of Maryland.

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Conclusion

Python is a very useful and powerful programming languages which bring a lot of benefits in a various fields of business.

A good language for a beginning programmers. It is good to all programmers at least to know

about Python, because Python is used everywhere in almost all the sectors like Web Development, Games, Graphics, Financial, Science, Software Development and Education.

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