python a practical perspective

PythonA practical perspective

Purpose

Show some Python characteristics

Identify scenarios where it can be used

Learn by examples

Foreword

Using a programming language doesn’t mean knowing everything about it

Experiment but focus on the purpose, not the language!

The Zen of Python (PEP* 20)

Beautiful is better than ugly.Explicit is better than implicit.Simple is better than complex.Complex is better than complicated.…* Python Enhancement Proposalhttp://legacy.python.org/dev/peps/pep-0020/

Multi paradigm language

Imperative

Object oriented

Functional

Indentation delimits blocks

Python C/C++/Java

if IsOk(): DoThatOne() DoAnotherOne()DoFinal()

if ( IsOk() ){ DoThatOne(); DoAnotherOne();}DoFinal();

Modules

import module_name…

module_name.module_function(...)module_name.variableDetails: https://docs.python.org/2/tutorial/modules.html

Functions

def MySum(param1, param2): result = param1 + param2 return result

Classes

class Derived(Base): def Method(self,...): …

Details: https://docs.python.org/2/tutorial/classes.html

Some built-in data types

int, float, long, complex, string, file

Lists: [ 1, “string”, 2.3 ]Dictionaries: { “Kate”:33 , “John”:25, “Deanna”:42 }Sets: set([1,2,1,6,7]) → [1,2,6,7]Tuple: (1, “Nigel”, 23)

Details: https://docs.python.org/2/library/stdtypes.html

Immutable objects

Cannot be changed after creation.Examples: numbers, strings, tuples (the minority)x = some immutable objecty = xy = … # change value of yx has the same valueDetails: https://docs.python.org/2/reference/datamodel.html and Please read [2]

Immutable objects (2)>>> x=39>>> y=x>>> y=41>>> print(x)39

>>> s1='Rob the bank!'>>> s2=s1>>> s2='Then take me home'>>> print(s1)Rob the bank!

>>> s="It's Python, ... yo!">>> s[2]='a'Traceback (most recent call last): File "<stdin>", line 1, in <module>TypeError: 'str' object does not support item assignment

Mutable objects

Can be changed after creationExamples: lists, dictionaries, classes (the majority)x = some mutable objecty = xy = … # change value of yx has changed its value

Mutable objects (2)>>> d1={"Deanna":"Nick Cave", "Jackie":"Placebo"}>>> d2=d1>>> d2["Jackie"]="Sinead O'Connor">>> print(d1){'Deanna': 'Nick Cave', 'Jackie': "Sinead O'Connor"}

>>> a1=['The Mono Jacks', 'Grimus', 'Urma']>>> a2=a1>>> a2.append('Byron')>>> print(a1)['The Mono Jacks', 'Grimus', 'Urma', 'Byron']

Some popular internal modules

Full list here https://docs.python.org/2.7/py-modindex.html

Coverage:● process/thread management - threading, subprocess● serialization/persistence - pickle, sqlite3, struct, bsddb, minidom● network communication - smtplib, poplib, ftplib, sockets, httplib,

urllib2, asyncore● encoding/compression - bz2, zlib, tarfile, zipfile, base64● file/directory handling - os, tempfile, os.path, stat● security - ssl, md5● string matching/parsing - re, fnmatch, ast

Some listed here: https://wiki.python.org/moin/UsefulModules

Coverage:● database handling - sqlalchemy, mysql-python● GUI - wxpython, pyqt● Scientific/Math functionality - NumPy, SciPy● Web development - django, web2py● Image processing - pil, pyqtgraph● Networking - tornado, twisted, Gevent● Process listing and manipulation - psutil

Some popular external modules

Enough, let’s walk the talk!

Code for this presentation

https://github.com/undergraver/PythonPresentation/

01_intro - some of Python’s characteristics02_typical - common Python usages03_demo - few polished examples04_regex - regular expressions in Python

Notes for examples

Please read the documentation for each python module used. Start from [3]

wxpythonUI uses wxpython [5] python library + wxformbuilder [7] for ui design

process list/kill uses psutil [6] python library

For regex is is recommended to read the documentation ( [4] )

Notable applications using Python

References[1] https://developers.google.com/edu/python/[2] http://www.slideshare.net/amiable_indian/introduction-to-python[3] https://docs.python.org/ [4] https://docs.python.org/2/library/re.html[5] http://www.wxpython.org/ [6] https://code.google.com/p/psutil/ [7] http://sourceforge.net/projects/wxformbuilder/