Python Programming Language

Python Programming Language

Created in 1991 by Guido Van Rossum

Python Programming Language

General Purpose Language Clean Syntax

Python Programming Language

General Purpose Language Clean Syntax Easy to Learn

Python Programming Language

General Purpose Language Clean Syntax Easy to Learn Easy to Debug

Python Programming Language

General Purpose Language Clean Syntax Easy to Learn Easy to Debug “Natural Feeling”

Python Programming Language

General Purpose Language Interpreted

Python Programming Language

General Purpose Language Interpreted

No Compilation Phase

Python Programming Language

General Purpose Language Interpreted

No Compilation Phase Multiplatform Integration

Python Programming Language

General Purpose Language Interpreted

No Compilation Phase Multiplatform Integration Native Debugger

Python Programming Language

General Purpose Language Interpreted Duck Typing

Python Programming Language

General Purpose Language Interpreted Duck Typing

Override behaviours by creating methods

Python Programming Language

General Purpose Language Interpreted Duck Typing

Override behaviours by creating methods Implement operations by creating

methodst

Python Programming Language

General Purpose Language Interpreted Duck Typing

Override behaviours by creating methods Implement operations by creating

methods All data is an object

Python Programming Language

Objects are Python’s 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.

Python Programming Language

An object’s 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

Python Programming Language

An object’s 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 object’s type is also unchangeable. The type() function returns an object’s

type (which is an object itself).

Python Programming Language

General Purpose Language Interpreted Duck Typing Strongly Typed

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.

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)

Functional Example

Pythonaddn = lambda n: lambda x: x + n

Ordef addN(n): def add_n(x): return x + n return add_n

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)))

Modular Design

The standard Python interpreter (CPython) is written in C89

It is designed with two-way interfacing in mind:Embedding C programs in PythonEmbedding Python programs in C

Modular DesignAn Example C Module#include <Python.h>

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( **** 'find . -name "*.py" **** -exec grep -Hn "Flying Circus" {} \;') ***********************************************************/

Cross Platform Execution

The CPython interpreter can be built on most platforms with a standard C library including

glibc and uclibc.

Cross Platform Execution

Interpreters such as Jython and IronPython can be used to run a python interpreter on

any Java or .NET VM respectively.

Python Is Good For

Protyping

Python Is Good For

ProtypingWeb Applications/SAS

Python Is Good For

ProtypingWeb Applications/SAS

Integration

Python Is Good For

ProtypingWeb Applications/SAS

IntegrationTransport Limited Applications

Python Is Good For

ProtypingWeb Applications/SAS

IntegrationTransport Limited ApplicationsIndeterminate Requirements

Python Is Good For

ProtypingWeb Applications/SAS

IntegrationTransport Limited ApplicationsIndeterminate requirements Short Relevence Lifetime

Python Is Good For

ProtypingWeb Applications/SAS

IntegrationTransport Limited ApplicationsIndeterminate requirements Short Relevence Lifetime

Porting Legacy Applications

Python Is Good For

ProtypingWeb Applications/SAS

IntegrationTransport Limited ApplicationsIndeterminate requirements Short Relevence Lifetime

Porting Legacy ApplicationsGlue

Python is Not Good For

Native Cryptography

Python is Not Good For

Native CryptographyMILOR

Python is Not Good For

Native CryptographyMILOR

Highly Parallel Design

__Types__

None

__Types__

None

NotImplemented

__Types__

NoneNotImplemented

Boolean

__Types__

NoneNotImplemented

Boolean

Int/LongInt

__Types__

NoneNotImplemented

BooleanInt/LongInt

Float (which is really a double)

__Types__

NoneNotImplemented

BooleanInt/LongInt

Float (which is really a double)

Complex (double +doubleJ)

__Types__

NoneNotImplemented

BooleanInt/LongInt

Float (which is really a double)Complex (double +doubleJ)

Sequences...

__Types__

Sequencesstring

unicodebytestuplelistset

frozenset

__Types__

NoneNotImplemented

BooleanInt/LongInt

Float (which is really a double)Complex (double +doubleJ)

Sequences...

Mapping Types (dict)

__Types__

NoneNotImplemented

BooleanInt/LongInt

Float (which is really a double)Complex (double +doubleJ)

Sequences...Mapping Types (dict)

Functions and Methods

__Types__

NoneNotImplemented

BooleanInt/LongInt

Float (which is really a double)Complex (double +doubleJ)

Sequences...Mapping Types (dict)

Functions and Methods

Generators

__Types__

NoneNotImplemented

BooleanInt/LongInt

Float (which is really a double)Complex (double +doubleJ)

Sequences...Mapping Types (dict)

Functions and MethodsGenerators

Modules

__Types__

NoneNotImplemented

BooleanInt/LongInt

Float (which is really a double)Complex (double +doubleJ)

Sequences...Mapping Types (dict)

Functions and MethodsGeneratorsModules

File/Buffer

__Types__

NoneNotImplemented

BooleanInt/LongInt

Float (which is really a double)Complex (double +doubleJ)

Sequences...Mapping Types (dict)

Functions and MethodsGeneratorsModules

File/Buffer

Type (metaclasses)

Special Duck Methods__abs__ __add____and____iter__

__getitem____iter____del__

__cmp__!__hash__

__lt__For Example

Example Codeclass Foo: baz = 'monkey' def bar(self): self.printFunc(self.text)

foo = Foo()foo.text = 'Hello World'

def print_console_factory( filter_func=lambda a: a ): def print_console(text): print(filter_func(text)) return print_console

foo.printFunc = print_console_factory()

print_hello_world = foo.barprint_hello_world()

>>> Hello World

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_vowels)

print_hello_world()

>>>Hll Wrld

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

Alternate Implementation

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

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

Alternate Implementation

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

Alternate Implementation

Psyco http://psyco.sourceforge.net Actually a C module Produces highly optimized C code from

python bytecode Excellent performance characteristics Configurable

Alternate Implementation

IronPython http://codesplex.com/Wiki/View.aspx?

ProjectName=IronPython 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

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

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

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

Hosting Python

mod_python By far most common hosting mechanism http://modpython.org Apache2 specific Interpreter embedded in webserver

worker Memory intensive Fast

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

Hosting Python

FastCGI Mature and stable Requires no 3rd party modules for most

webservers Fast and inexpensive Sandboxing supported

Hosting Python

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

requirements Slow

Web Frameworks

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

Web Frameworks

Django Data Layer Business Logic Control Layer Presentation Layer

Not just for the web

Web Frameworks

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

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

Web Frameworks

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

Web Frameworks

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