Python Programming Language

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Python Programming Language
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Python Programming Language

• Created in 1991 by Guido Van Rossum

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Python Programming Language

• General Purpose Language
• Clean Syntax

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Python Programming Language

• General Purpose Language
• Clean Syntax
• Easy to Learn

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Python Programming Language

• General Purpose Language
• Clean Syntax
• Easy to Learn
• Easy to Debug

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Python Programming Language

• General Purpose Language
• Clean Syntax
• Easy to Learn
• Easy to Debug
• Natural Feeling

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Python Programming Language

• General Purpose Language
• Interpreted

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Python Programming Language

• General Purpose Language
• Interpreted
• No Compilation Phase

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Python Programming Language

• General Purpose Language
• Interpreted
• No Compilation Phase
• Multiplatform Integration

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Python Programming Language

• General Purpose Language
• Interpreted
• No Compilation Phase
• Multiplatform Integration
• Native Debugger

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Python Programming Language

• General Purpose Language
• Interpreted
• Duck Typing

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Python Programming Language

• General Purpose Language
• Interpreted
• Duck Typing
• Override behaviours by creating methods

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Python Programming Language

• General Purpose Language
• Interpreted
• Duck Typing
• Override behaviours by creating methods
• Implement operations by creating methodst

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Python Programming Language

• General Purpose Language
• Interpreted
• Duck Typing
• Override behaviours by creating methods
• Implement operations by creating methods
• All data is an object

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Python Programming Language

• Objects are Pythons abstraction for data. All
  data in a Python program is represented by
  objects or by relations between objects.
• Every object has an identity, a type and a value.
  

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Python Programming Language

• An objects identity never changes once it has
  been created
• The is operator compares the identity of two
  objects
• The id() function returns an integer representing
  its identity

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Python Programming Language

• An objects identity never changes once it has
  been created
• The is operator compares the identity of two
  objects
• The id() function returns an integer representing
  its identity
• An objects type is also unchangeable.
• The type() function returns an objects type
  (which is an object itself).

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Python Programming Language

• General Purpose Language
• Interpreted
• Duck Typing
• Strongly Typed

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Python Programming Language

• A Python programmer can write in any style they
  like, using design patterns borrowed from
• Imperative
• Declarative
• Object Oriented
• functional programming
• The author is free let the problem guide the
  development of the solution.

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Python Programming Language

• print('hello world')

• class Hello(object)
• def __init__(self, my_string)
• self.my_string my_string
• def __call__(self, render_func)
• out_str 'Hello s' self.my_string
• render_func(out_str)
• def print_string(string_to_print)
• print(string_to_print)
• myHelloWorldClass Hello('world')
• myHelloWorldClass(print_string)

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Functional Example

• Java
• public class OuterClass
• // Inner class
• class AddN
• AddN(int n) _n n
• int add(int v) return _n v
• private int _n
• public AddN createAddN(int var)
• return new AddN(var)

• LISP
• (define (addn n) (lambda (k) ( n k)))

Python addn lambda n lambda x x n Or def
addN(n) def add_n(x) return x n
return add_n
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Modular Design

• The standard Python interpreter (CPython) is
  written in C89
• It is designed with two-way interfacing in mind
• Embedding C programs in Python
• Embedding Python programs in C

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Modular Design

• An Example C Module
• include ltPython.hgt
• static PyObject
• spam_system(PyObject self, PyObject args)
• const char command
• int sts
• if (!PyArg_ParseTuple(args, "s", command))
• return NULL
• sts system(command)
• return Py_BuildValue("i", sts)
• /
  
• import spam
  
• spam.system(
  

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Cross Platform Execution

• The CPython interpreter can be built on most
  platforms with a standard C library including
  glibc and uclibc.

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Cross Platform Execution

• Interpreters such as Jython and IronPython can be
  used to run a python interpreter on any Java or
  .NET VM respectively.

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Python Is Good For

• Protyping

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Python Is Good For

• Protyping
• Web Applications/SAS

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Python Is Good For

• Protyping
• Web Applications/SAS
• Integration

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Python Is Good For

• Protyping
• Web Applications/SAS
• Integration
• Transport Limited Applications

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Python Is Good For

• Protyping
• Web Applications/SAS
• Integration
• Transport Limited Applications
• Indeterminate Requirements

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Python Is Good For

• Protyping
• Web Applications/SAS
• Integration
• Transport Limited Applications
• Indeterminate requirements
• Short Relevence Lifetime

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Python Is Good For

• Protyping
• Web Applications/SAS
• Integration
• Transport Limited Applications
• Indeterminate requirements
• Short Relevence Lifetime
• Porting Legacy Applications

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Python Is Good For

• Protyping
• Web Applications/SAS
• Integration
• Transport Limited Applications
• Indeterminate requirements
• Short Relevence Lifetime
• Porting Legacy Applications
• Glue

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Python is Not Good For

• Native Cryptography

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Python is Not Good For

• Native Cryptography
• MILOR

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Python is Not Good For

• Native Cryptography
• MILOR
• Highly Parallel Design

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__Types__

• None

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__Types__

• None
• NotImplemented

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__Types__

• None
• NotImplemented
• Boolean

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__Types__

• None
• NotImplemented
• Boolean
• Int/LongInt

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__Types__

• None
• NotImplemented
• Boolean
• Int/LongInt
• Float (which is really a double)

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__Types__

• None
• NotImplemented
• Boolean
• Int/LongInt
• Float (which is really a double)
• Complex (double doubleJ)

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__Types__

• None
• NotImplemented
• Boolean
• Int/LongInt
• Float (which is really a double)
• Complex (double doubleJ)
• Sequences...

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__Types__

• Sequences
• string
• unicode
• bytes
• tuple
• list
• set
• frozenset

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__Types__

• None
• NotImplemented
• Boolean
• Int/LongInt
• Float (which is really a double)
• Complex (double doubleJ)
• Sequences...
• Mapping Types (dict)

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__Types__

• None
• NotImplemented
• Boolean
• Int/LongInt
• Float (which is really a double)
• Complex (double doubleJ)
• Sequences...
• Mapping Types (dict)
• Functions and Methods

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__Types__

• None
• NotImplemented
• Boolean
• Int/LongInt
• Float (which is really a double)
• Complex (double doubleJ)
• Sequences...
• Mapping Types (dict)
• Functions and Methods
• Generators

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__Types__

• None
• NotImplemented
• Boolean
• Int/LongInt
• Float (which is really a double)
• Complex (double doubleJ)
• Sequences...
• Mapping Types (dict)
• Functions and Methods
• Generators
• Modules

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__Types__

• None
• NotImplemented
• Boolean
• Int/LongInt
• Float (which is really a double)
• Complex (double doubleJ)
• Sequences...
• Mapping Types (dict)
• Functions and Methods
• Generators
• Modules
• File/Buffer

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__Types__

• None
• NotImplemented
• Boolean
• Int/LongInt
• Float (which is really a double)
• Complex (double doubleJ)
• Sequences...
• Mapping Types (dict)
• Functions and Methods
• Generators
• Modules
• File/Buffer
• Type (metaclasses)

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Special Duck Methods

• __abs__
• __add__
• __and__
• __iter__
• __getitem__
• __iter__
• __del__
• __cmp__!
• __hash__
• __lt__
• For Example

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Example Code

• class Foo
• baz 'monkey'
• def bar(self)
• self.printFunc(self.text)
• foo Foo()
• foo.text 'Hello World'
• def print_console_factory(
• filter_funclambda a a
• )
• def print_console(text)
• print(filter_func(text))
• return print_console
• foo.printFunc
• print_console_factory()
• print_hello_world foo.bar

• vowels 'a', 'e', 'i', 'o', 'u'
• filter_vowels lambda a
• ''.join( let
• for let in a
• if not
• let.lower() in vowels
• )
• foo.printFunc print_console_factory(filter_vowel
  s)
• print_hello_world()
• gtgtgtHll Wrld

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Python Resources

• Python.org Documentation
• http//www.python.org
• Python.org PEPs
• http//www.python.org/dev/peps/
• Ye Olde Cheese Shoppe
• http//pypi.python.org/pypi

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Alternate Implementation

• C API
• http//docs.python.org/extending
• Create C Modules
• Execute Python within a C application
• Interface via a C API

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Alternate Implementation

• Jython
• http//www.jython.org/Project
• Native JVM Python interpreter
• Full support for standard library
• Other C Extensions may not be ported
• Python extensions may rely on C extensions

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Alternate Implementation

• PyPy
• http//codespeak.net/pypy/dist/pypy/doc/
• Python interpreter written in python
• Framework interprets multiple languages
• Highly extendable
• Slow

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Alternate Implementation

• Psyco
• http//psyco.sourceforge.net
• Actually a C module
• Produces highly optimized C code from python
  bytecode
• Excellent performance characteristics
• Configurable

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Alternate Implementation

• IronPython
• http//codesplex.com/Wiki/View.aspx?ProjectNameIr
  onPython
• Native python interpreter (C) for .NET
• Full support for standard library
• Many external modules have been ported
• Porting modules is quite simple
• Can integrate with .NET languages

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Alternate Implementation

• PyJamas
• http//code.google.com/p/pyjamas/
• Python interpreter for JavaScript
• Cross browser fully supported
• As lightweight as you'd think
• JSON/JQuery may be a better option

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Alternate Implementation

• ShedSkin
• http//code.google.com/p/shedskin/
• Produces C code from Python code
• Excellent for prototyping
• Some language features not supported
• Implicit static typed code only

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Alternate Implementation

• Cython
• http//www.cython.org
• Embed C code in a python application
• Excellent for use in profiling
• Compiled at first runtime
• Shared build env with python interpreter

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Hosting Python

• mod_python
• By far most common hosting mechanism
• http//modpython.org
• Apache2 specific
• Interpreter embedded in webserver worker
• Memory intensive
• Fast

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Hosting Python

• WSGI
• Up and coming for a good reason
• http//code.google.com/p/modwsgi/
• http//code.google.com/p/isapi-wsgi/
• Can embedded interpreter
• Can run threaded standalong app server
• Very fast and inexpensive
• Sandboxing supported

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Hosting Python

• FastCGI
• Mature and stable
• Requires no 3rd party modules for most webservers
• Fast and inexpensive
• Sandboxing supported

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Hosting Python

• CGI
• Mature and stable
• Supported on nearly all platforms
• Very flexible in terms of hosting requirements
• Slow

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Web Frameworks

• Django
• http//www.djangoproject.com/
• Active user community
• Well documented
• Currently under active development
• Extensive meta and mock classes
• Clean layer separation

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Web Frameworks

• Django
• Data Layer
• Business Logic
• Control Layer
• Presentation Layer
• Not just for the web

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Web Frameworks

• Turbogears CherryPy
• http//www.turbogears.org
• Persistent app server
• Javascript integration via mochikit
• Flexible DB backend via SQLObject

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Web Frameworks

• Pylons - Paste
• http//www.pylonshq.org/
• Multiple DB Backends supported
• Multiple templating languages pluggable
• Multiple request dispatching
• HTTP oriented
• Forward compatible
• MVC Type layer separation

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Web Frameworks

• Zope
• http//www.zope.org
• Web Application Framework
• Highly Web Oriented
• Not lightweight
• Highly Featureful
• ZDB Data store backend

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Web Frameworks

• Zope
• http//www.zope.org
• Web Application Framework
• Highly Web Oriented
• Not lightweight
• Highly Featureful
• ZDB Data store backend