Download Python Application Development

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)
Java:
Functional Example
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
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
Modular Design
An 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
Protyping
Web Applications/SAS
Python Is Good For
Protyping
Web Applications/SAS
Integration
Python Is Good For
Protyping
Web Applications/SAS
Integration
Transport Limited Applications
Python Is Good For
Protyping
Web Applications/SAS
Integration
Transport Limited Applications
Indeterminate Requirements
Python Is Good For
Protyping
Web Applications/SAS
Integration
Transport Limited Applications
Indeterminate requirements
Short Relevence Lifetime
Python Is Good For
Protyping
Web Applications/SAS
Integration
Transport Limited Applications
Indeterminate requirements
Short Relevence Lifetime
Porting Legacy Applications
Python Is Good For
Protyping
Web Applications/SAS
Integration
Transport Limited Applications
Indeterminate requirements
Short Relevence Lifetime
Porting Legacy Applications
Glue
Python is Not Good For
Native Cryptography
Python is Not Good For
Native Cryptography
MILOR
Python is Not Good For
Native Cryptography
MILOR
Highly Parallel Design
__Types__
None
__Types__
None
NotImplemented
__Types__
None
NotImplemented
Boolean
__Types__
None
NotImplemented
Boolean
Int/LongInt
__Types__
None
NotImplemented
Boolean
Int/LongInt
Float (which is really a double)
__Types__
None
NotImplemented
Boolean
Int/LongInt
Float (which is really a double)
Complex (double +doubleJ)
__Types__
None
NotImplemented
Boolean
Int/LongInt
Float (which is really a double)
Complex (double +doubleJ)
Sequences...
__Types__
Sequences
string
unicode
bytes
tuple
list
set
frozenset
__Types__
None
NotImplemented
Boolean
Int/LongInt
Float (which is really a double)
Complex (double +doubleJ)
Sequences...
Mapping Types (dict)
__Types__
None
NotImplemented
Boolean
Int/LongInt
Float (which is really a double)
Complex (double +doubleJ)
Sequences...
Mapping Types (dict)
Functions and Methods
__Types__
None
NotImplemented
Boolean
Int/LongInt
Float (which is really a double)
Complex (double +doubleJ)
Sequences...
Mapping Types (dict)
Functions and Methods
Generators
__Types__
None
NotImplemented
Boolean
Int/LongInt
Float (which is really a double)
Complex (double +doubleJ)
Sequences...
Mapping Types (dict)
Functions and Methods
Generators
Modules
__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
__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)
Special Duck Methods
__abs__
__add__
__and__
__iter__
__getitem__
__iter__
__del__
__cmp__!
__hash__
__lt__
For Example
Example Code
class 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.bar
print_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
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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
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Produces highly optimized C code from
python bytecode

Excellent performance characteristics

Configurable
Alternate Implementation

IronPython

http://codesplex.com/Wiki/View.aspx?Proj
ectName=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