Python: The Dynamic!

csccit2011 University of Tabriz by Omid Mogharian omid.mogharian@gmail.com

outline •  •  •  •  •  •  What is python? Why python? Introduction to python Python programming: Tips & Tricks More on python Scienti"c module

What is python? •  Python is a Interpreted, Interactive, Portable, Functional / Object-Oriented programing language. •  Invented by “Guido Van Rossum” in 1991. •  free and open source develop by “python software foundation”, available at www.python.org •  "nal release: Python 2.7.2 , python 3.2.2

Why python? •  •  •  •  •  •  Multi purpose design (web, os. application ,scienti"c, …) Cross platform (wide portability) Both Functional & O.O programming Rapid in Prototyping, strong in enterprise system Integrate with other languages (c/c++, java, fortran, …) Dynamic, Extensible, readable.

Why python? •  •  •  •  •  •  Many library and module Easy to use (simple & familiar syntax ,few restrictions & rules) Automatic memory management (Garbage Collector) Good element (Dictionary, List, … ) Good built-in algorithms (hashing , sorting , …) Many companies & institutions around the world use python (Google, Yahoo, NASA, YouTube, FriendFeed , …)

Introduction to python •  Start with python –  Set up •  Linux , mac os X. and most operating systems have Python •  For windows, download python installer and run it. –  Run •  Use interactive mode by type “python” in Terminal •  “python ["lename].py” run python code "les –  lDE •  Every text editor with a little understanding of code : notepad++,Gedit, jedit, … •  IDLE python editor releasing by “python.org” •  KOMODO is a good one!

Introduction to python •  Strings –  Concatenation “Hello” + “World” -> “HelloWorld” –  Repetition “Tabrizu” * 3 -> “TabrizuTabrizuTabrizu” –  Indexing “Tabrizu”[2] ->“b” , “Tabrizu”[-2] -> “z” –  Slicing “Tabrizu”[1:4] -> “abri” –  Size len(“Tabrizu”)-> 7 –  Comparison “Tabrizu” > “tabrizu” -> fasle –  Search “u” in “Tabrizu” -> true

Introduction to python •  Lists –  e.g. aList = [631, “python”, [331, “tb”]] –  Like indexable arrays, not like linked list –  Same operators as for strings –  More operations append(), insert(), pop(), reverse() and sort() •  Sets –  e.g. aSet=set([‘tabrizu’,’ploytechnic’,’tehran’]) –  add(x), remove(x), discard(x), pop(), clear(), issubset(), issuperset(), … –  Union ‘|’, intersection ‘&’, di#erence ‘#’

Introduction to python •  Tuples –  e.g. aTuple = (631, “python”, (611, “SA”)) –  Unlike lists and like strings & set tuples are immutable •  Dic6onaries –  e.g. adict= {“tabriz”:”python”,”tehran”:”Java”} –  Lookup adict[“tabriz”] -> ”python” –  Insert adict[“value”] = 100 –  Delete del adict[“value”] –  Presencie adict.has_key(“tehran”) -> True –  Itera6ons keys(), values(), items()

Introduction to python •  Variables –  No need to declare, Not typed but need to initialize –  Almost everything can be assigned to a variable (functions, modules, classes) –  All variable are reference (a=b means a & b refer to same object) •  Flow of Control –  if condition : statements (elif condition : statements) [else : statements] –  while condition : statements [else : statements] –  for var in sequence : statements [else : statements] –  Break & Continue

Introduction to python •  Functions –  def FunctionName(arg1, arg2, ...): Statements return (expression) •  Classes –  class ClassName(BaseClass1, BaseClass2...) : Statements –  x = ClassName() creates a new instance

Introduction to python •  A simple example

Introduction to python > this is a static function!

Introduction to python > omid!

Introduction to python > AttributeError: cls instance has no attribute 'name’!

Introduction to python > len of prob is 1 and this is a external function!

Introduction to python > this is overwrite function!

Introduction to python > <__main__.cls instance at 0x10aeac440>!

Introduction to python •  Modules –  Usage: e.g. import datetime –  Partial usage: e.g. from datetime import time –  bult-in , installed and beside of code .py "les modules •  example > Python test.py jim! > Hello jim!

Tips & Tricks None and empty cheaking my_object = 'Test' # True example! # my_object = '' or my_object = None # False example! if len(my_object) > 0:! !print 'my_object is not empty'! ! if len(my_object): # 0 will evaluate to False! print 'my_object is not empty’! if my_object != '':! print 'my_object is not empty’! ! if my_object: # an empty string will evaluate to False! print 'my_object is not empty'

Tips & Tricks Divition and $oat numbers 5/2 5.0/2 float(5)/2 5//2 ! # # # # Returns Returns Returns Returns 2! 2.5! 2.5! 2! from __future__ import division! 5/2 # Returns 2.5! 5.0/2 # Returns 2.5! float(5)/2 # Returns 2.5! 5//2 # Returns 2

Tips & Tricks In one line! list= [’tabriz', ’tehran', ’shiraz']! print 'The three are: %s.' % ', '.join(list)! # print the tree are tabriz, tehran, shiraz! ! validation= True if list else 'Test is False'! # validation is True! ! ! ! ! !

Tips & Tricks lambda def add(a,b): return a+b! add2 = lambda a,b: a+b squares = map(lambda a: a*a, [1,2,3,4])! Squares = a*a for a in [1,2,3,4]! squares is now [1,4,9,16]

Tips & Tricks Lambda & one line for numbers = [1,2,3,4,5]! numbers_under_4 = filter(lambda x: x < 4, numbers)! numbers_under_4 = [number for number in numbers if number < 4]! # numbers_under_4 = [1,2,3]! ! squares = map(lambda x: x*x, filter(lambda x: x < 4, numbers))! squares = [number*number for number in numbers if number < 4]! # square is now [1,4,9]

Tips & Tricks one line for Vs nested for print [(x, y, x * y) for x in (0,1,2,3) for y in (0,1,2,3) if x < y]! # prints [(0, 1, 0), (0, 2, 0), (0, 3, 0), (1, 2, 2), (1, 3, 3), (2, 3, 6)]! ! for x in (0,1,2,3):! for y in (0,1,2,3):! if x < y:! print (x, y, x*y),! # prints (0, 1, 0) (0, 2, 0) (0, 3, 0) (1, 2, 2) (1, 3, 3) (2, 3, 6)! !

Tips & Tricks Lambda … numbers = [1,2,3,4,5]! ! result = reduce(lambda a,b: a*b, numbers)! ! result = 1! for number in numbers:! !result *= number! ! # result is now 120

Tips & Tricks …. ! ! strings = ['a', 'b', 'c', 'd', 'e’]! for index, string in enumerate(strings):! print index, string,! # prints '0 a 1 b 2 c 3 d 4 e’! ! numbers = [1,10,100,1000,10000]! if any(number < 10 for number in numbers):! print 'Success’! # Output: 'Success!'

Tips & Tricks …. ! ! if all(number < 10 for number in numbers):! print 'Success!’! # Output: (nothing)! ! ! test = True! result = ['Test is False','Test is True'][test]! # result is now 'Test is True’!

Tips & Tricks Default value ! def function(item, stuff = []):! stuff.append(item)! print stuff! ! function(1)! # prints '[1]’! function(2)! # prints '[1,2]' !!!! ! ! !

Tips & Tricks Arbitrary Numbers of Arguments ! ! ! def do_something_else(a, b, c, *args, **kwargs):! print a, b, c, args, kwargs! ! ! do_something_else(1,2,3,4,5,6,7,8,9, timeout=1.5)! # prints '1, 2, 3, (4, 5, 6, 7, 8, 9), {"timeout": 1.5}'!

Tips & Tricks Decorator def decorator1(func):! return lambda: func() + 1! def decorator2(func):! def print_func():! print func()! return print_func! ! @decorator2! @decorator1! def function():! return 41! function()! ! function = decorator2(decorator1(function))! # prints '42'

Tips & Tricks ! Dict / Object ! class mydict(dict):! def __getattr__(self, attr):! if super(mydict,self).has_key(attr):! return super(mydict,self).__getitem__(attr)! ! def __setattr__(self,attr,value):! super(mydict,self).__setattr__(attr,value)! ! adict= {‘apple’:1 ,’banana’:2 , ‘peach’:3}! mdict=mydict(adict)! mdict.orange=10! print mdict.apple, mdict.orange , mdict[‘banana’] , mdict! # prints '1 ! 10 2 {‘apple’:1 ,’banana’:2 , ‘peach’:3 , ‘orange’:10}’!

More on python •  Commercial Usage –  –  –  –  MVC Web programming via web server modules: Tornado, cherrypy ,… Mobile programming :PyObjC, ASE , … Easily connect to famous DB: MSSQL, Mysql , Oracle,… designed for non-relational DB linke Cassandra, MongoDB, CouchDB. What is Non-relational DB!? •  No relation between data, Provide list, vector, nested data "elds •  No force schema & type •  Java script base syntax instead of SQL •  Document-oriented , Key-Value and Object-oriented database

More on python •  Integrating Python With Other Languages –  SWIG - generate extension module from your .h "les –  F2PY - Fortran to Python Interface Generator –  Lython (archived page) - Lisp front-end for Python –  JPype Java for CPython •  Python interpreters –  Cpython a bytecode interpreter (Orginal) –  –  –  –  PyPy a JIT Compiler, more Speed & eﬃciency ShedSkin a Python to C++ programming language compiler Jython a Java implemented of Python ironpython a .net implemented of python

Scienti"c module •  Numeric Module –  NumPy Numerical Python adds a fast, compact, mul6dimensional array facility to Python –  SciPy Includes modules for linear algebra, op6miza6on, integra6on, special func6ons, sta6s6cs, and others. –  OpenOpt a framework for numerical op6miza6on and systems of linear/ non-‐linear equa6ons. –  ALGLIB numerical analysis library in C++ and C#, with Python interfaces. –  SpaceFuncs -‐ a tool for 2D, 3D, N-‐dimensional geometric modeling with possibili6es of parametrized calcula6ons, numerical op6miza6on and solving systems of geometrical equa6ons with automa6c diﬀeren6a6on.

Scienti"c module •  Algorithm Module –  Mlpy Machine Learning Python and high-‐performance Python module for Predic6ve Modeling –  SciPy for signal and image processing, gene6c algorithms –  graph-‐tool A python module for eﬃcient analysis of graphs (aka. Networks) –  Pyevolve is evolutionary algoritm. Machin learning.

Scienti"c module •  Grid CompuAng Module –  PyGlobus Globus toolkit bindings for python –  PEG Python Extensions for the Grid –  Ganga Grid job management interface. –  DIANE Python user-‐level middleware layer for Grids.

Scienti"c module •  Other ScienAfic Module –  ScienAficPython is a collec6on of Python scien6fic modules –  Thuban is a Python Interac6ve Geographic Data Viewer –  Matplotlib hp://matplotlib.sourceforge.net/ -‐ matplotlib is a python 2D plo]ng library –  Biopython -‐ a set of freely available tools for biological computa6on and bioinforma6cs. –  PyMol 3D molecular viewer

Scienti"c module •  Exmaple Usige Pyevolve –  Installing pakages > apt-‐get install python-‐setuptools! > easy_install pyevolve! Or instal .egg pakage > easy_install /downloads/downloaded_package.egg !

Scienti"c module •  Exmaple Usige Pyevolve

Refrences •  Python Homepage hJp://www.python.org/ •  Python wiki hJp://wiki.python.org/ •  Google Code University hJp://code.google.com/edu/ •  Python documentaAon hJp://docs.python.org/

Python: The Dynamic!

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Python: The Dynamic!