Programming at the speed of lightPythonismKracekumar.Rkracethekingmaker@gmail.com

- needs Software Freedom Day@Alexandria University

Agenda

What is Python ???

Why Python ???

Syntax Walkthroughs

Linux and Python

What is Python ???

What is Python ???

Why Python ???

Syntax Walkthroughs

Linux and Python

History

Created by Guido von Rossum in 1990 (BDFL)

named after Monty Python's Flying Circus

http://www.python.org/~guido/

Blog http://neopythonic.blogspot.com/

Now works for Google

What is Python ???

general-purpose high-level programming language, often used as a scripting language.

interpreted, interactive, object-oriented.

incorporates modules, exceptions, dynamic typing, very high level dynamic data types, and classes, automatic memory management.

remarkable power with very clear syntax.

has interfaces to many system calls and libraries, as well as to various window systems, and is extensible in C or C++.

What is Python ???

supports multiple programming paradigms (primarily object oriented, imperative, and functional)

portable: runs on many Unix variants, on the Mac, and on PCs under MS-DOS, Windows, Windows NT, OS/2, FreeBSD Solaris, OS/2, Amiga,AROS, AS/400, BeOS, OS/390, z/OS, Palm OS, QNX, VMS, Psion, Acorn RISC OS, VxWorks, PlayStation, Sharp Zaurus, Windows CE and even PocketPC !

What is Python ???

Developed and supported by a large team of volunteers - Python Software Foundation

Major implementations: CPython, Jython, Iron Python, PyPy

CPython - implemented in C, the primary implementation

Jython - implemented for the JVM

Pypy - implemented in Python

IronPython - implemented in C#, allows python to use the .NET libraries

Why Python ???

What is Python ???

Why Python ???

Syntax Walkthroughs

Linux and Python

Why Python ???

Readability, maintainability, very clear readable syntax

Fast development and all just works the first time...

very high level dynamic data types

Dynamic typing and automatic memory management

Free and open source

Implemented under an open source license. Freely usable and distributable, even for commercial use.

Simplicity , Great first language

Availability (cross-platform)

Interactivity (interpreted language)

Why Python ???

GUI support GUIs typically developed with Tk

Strong introspection capabilities

Intuitive object orientation

Natural expression of procedural code

Full modularity, supporting hierarchical packages

Exceptionbased error handling

The ability to be embedded within applications as a scripting interface

Scalable can play nicely with other languages

Batteries Included

The Python standard library is very extensive

regular expressions, codecs

date and time, collections, threads and mutexs

OS and shell level functions (mv, rm, ls)

Support for SQLite and Berkley databases

zlib, gzip, bz2, tarfile, csv, xml, md5, sha

logging, subprocess, email, json

httplib, imaplib, nntplib, smtplib

and much, much more ...

Python Libraries

Biopython - Bioinformatics

SciPy - Linear algebra, signal processing

NumPy - Fast compact multidimensional arrays

PyGame - Game Development

Visual Python - real-time 3D output

Django - High-level python Web framework

and much more ...

E.g. Projects with Python

Websites: Google, YouTube, Yahoo Groups & Maps, CIA.gov

Appengine:http://code.google.com/appengine/

Google: Python has been an important part of Google since the beginning., Peter Norvig.

Python application servers and Python scripting to create the web UI for BigTable (their database project)

Systems: NASA, LALN, CERN, Rackspace

Nasa Nebula http://nebula.nasa.gov/about

Games: Civilization 4, Quark (Quake Army Knife)

Mobile phones: Nokia S60 (Symbian), PythonCE

P2P: BitTorrent

Cont . . .

Maya, a powerful integrated 3D modeling and animation system, provides a Python scripting API.

EVE Online, a Massively Multi player Online Game (MMOG), makes extensive use of Python.

iRobot uses Python to develop commercial robotic devices.

What can you do with Python

Systems Programming

GUI

Internet Scripting

Database Programming

Numeric and Scientific Programming

Natural language analysis

What people say about Python ?

I can remember many Python idioms because

they're simpler. That's one more reason I program faster [in Python]. I still have to look up how to open a file every time I do it in Java. In fact, most things in Java require me to look something up.--Bruce Eckel

Cont . . .

Python ... is compact -- you can hold its entire

feature set (and at least a concept index of its libraries) in your head.

-- Eric S. Raymond

Syntax Walkthroughs

What is Python ???

Why Python ???

Syntax Walkthroughs

Linux and Python

Talk is cheap. Show me the code.

Linus Torvaldus

Hello World

Python 2.6

Python 3.0

print(Hello World) print Hello World

Starting python

Open terminal and Enter python and hit enter

Something like thiskracekumar@kracekumar-laptop:~$ pythonPython 2.6.4 (r264:75706, Dec 7 2009, 18:45:15) [GCC 4.4.1] on linux2Type "help", "copyright", "credits" or "license" for more information.>>>

Interactive shell

>>> 2+3

5

>>> 2*3

6

>>> 2/3

0

>>> 2//3

0

Interactive Shell cont . . .

>>> 2.0/3.0

0.66666666666666663

>>> 2.0/3

0.66666666666666663

>>> 2/3.0

0.66666666666666663

>>> 2-3

-1

Interactive shell Cont . . .

>>> complex(3,4)

(3+4j)

>>> 5+4j+5+6j

(10+10j)

>>> pow(4,5)

1024

>>> 4**5

1024

Math More

>>> 3%4

3

>>> long(34.999999)

34L

>>> int(34.9999)

34

>>> str(5)

'5'

Still more Interactive shell

>>> chr(45)

'-'

>>> ord('a')

97

You can do more in interactive shell ,But you might be bored,so Lets start writing small scripts

First program

Open first.py

Run python first.py ,Your program will be interpreted and python will produce .pyc in memory .

.pyc =>python compiled

Duck typed programming language

Interactive Shell (Revisited)

>>> b='0x123'

>>> type(b)

>>> b=23

>>> type(b)

>>> c=32L

>>> type(c)

Cont . . .

>>> c=2**890

>>> c

8254602048994769474255309139320571976856989469314398783249386078541779727448825929287769623244643560854287421769642635607536680617229461519539671538483430889193541937484454440136429963694163141453503639190799818814812942074243152169349951543234944945149040326527156224L

>>> len(str(c))

268

Str() =>Find string length

String

>>> name='krace'

>>> name1="krace"

>>> name2="""krace"""

>>> name3='''krace'''

>>> name

'krace'

>>> name1

'krace'

>>> name2

'krace'

>>> name3

'krace'

Importing in built modules

Open try_import .py

Strings

>>> name="kracekumar"

>>> name[1:]

'racekumar'

>>> name[:1]

'k'

>>> name[:5]

'krace'

>>> name[:-5]

'krace'

Strings are immutable

>>> name[0]="a"

Traceback (most recent call last):

File "", line 1, in

TypeError: 'str' object does not support item assignment

>>> name

'kracekumar'

>>> name="K"+name[1:]

>>> name

'Kracekumar'

Above is a small hack to change the first character value in the name

Slicing

>>> name[1:5]

'race'

>>> name + " likes linux " #concatenation

'Kracekumar likes linux '

>>> name.startswith('k')

False

>>> name.upper()

'KRACEKUMAR'

Python introspection

Python introspection lets you to find all builtin functions,classes etc. . .

>>> dir()

['__builtins__', '__doc__', '__name__', '__package__', 'a', 'b', 'c', 'name', 'name1', 'name2', 'name3', 'sys']

dir(anyname) =>will yield all the supported functions.

In Built help

help(anyname)

>>> help(a)

no Python documentation found for '123'#here no documentation is available so you won't findhelp(sys)

Find the magic here :)

Data structure

3 in built data structure

List => a=[1,linux,2,Free Bsd]

Tuple => b=(1,apple,mango)#mango is not quoted because here it refers variable

Dictionary =>dict={name:kracekumar,email:kracethekingmaker@gmail.com,coll:Amrita}

Don't worry guys you have array but i will introduce later

Data structure

>>> a

[1, 'linux', 2, 'Free Bsd']

>>> b

(1, 'apple', 'mango')

>>> dict

{'coll': 'Amrita', 'name': 'kracekumar', 'email': 'kracethekingmaker@gmail.com'}

List is not linked list here

You can have string ,int,float in list,tuple,dictionary

Data structure in python

>>> type(a)

>>> type(b)

>>> type(dict)

Tuple is immutable

Cont . . .

>>> a[1]

'linux'

>>> a[1]="UBuntu"

>>> a[1]

'UBuntu'

>>> a

[1, 'UBuntu', 2, 'Free Bsd']

Cont . . .

>>> b[1]

'apple'

>>> b[1]="pine apple"

Traceback (most recent call last):

File "", line 1, in

TypeError: 'tuple' object does not support item assignment

>>> b

(1, 'apple', 'mango')

Dictionary

>>> dict

{'coll': 'Amrita', 'name': 'kracekumar', 'email': 'kracethekingmaker@gmail.com'}

coll =>is key and 'Amrita' =>value

All key should be unique

>>> dict['coll']="ASE"

>>> print dict

{'coll': 'ASE', 'name': 'kracekumar', 'email': 'kracethekingmaker@gmail.com'}

>>> dir(dict)

Dictionary functions

dir() and help() will help you to know more about list tuple

dir(dict)

Tryhas_key()

Pop()

Items()

Slicing holds for list and tuples

Control Flow

if guess == number: #do somethingelif guess < number: #do something elseelse: #do something else

while True: #do something #break when done breakelse: #do something when the loop endsfor i in range(1, 5): print(i)else: print('The for loop is over')#1,2,3,4for i in range(1, 5,2): print(i)else: print('The for loop is over')#1,3

Program

Wap to find a no is prime or not

List comprehension

E.g >>> x=[y for y in range(0,20) if y%2 == 0]

>>> x

[0, 2, 4, 6, 8, 10, 12, 14, 16, 18]

Alternate way to do

Open list_comp.py

Dictionaries,list,tuple can be nested

Functions

Order is important unless using the name

Default arguments are supported

def sayHello(): print('Hello World!')def foo(name, age, address) :pass

foo('Tim', address='Home', age=36) def greet(name='World')

Functions

Variable length args acceptable as a list or dict

def total(initial=5, *numbers, **keywords): count = initial for number in numbers: count += number for key in keywords: count += keywords[key] return countprint(total(10, 1, 2, 3, vegetables=50, fruits=100))

Functions

def printMax(x, y): '''Prints the maximum of two numbers. The two values must be integers.''' x = int(x) # convert to integers, if possible y = int(y) if x > y: return x else: return yprintMax(3, 5)

Last important thing about variable

>>> a=[1,2,3]

>>> b=a

>>> a[0]=4

>>> b

[4, 2, 3]

>>> a

[4, 2, 3]

If you want to have copy of a list use slice or import copy(use dir and find out)

File Handling

Wap to read input from user and write back to file . =>fav_movie.py

Wap to read set of numbers and write to file and read the file and add all the nos.=>pickling.py

Swap 3 nos

Practice problem

Get a particular line from a file = >get_particular_line.py

Get a list of zip file content and its size =>zip_length.py

Get current system name and ip=>details.py

Generate a random password using python

Modules

Any python file is considered a module

Modules can be imported or run by themselves

if __name__ == '__main__': print('This program is being run by itself')else: print('I am being imported from another module')

Recursion

>>> def mysum(L):

... if not L:

... return 0

... else:

# Call myself

... return L[0] + mysum(L[1:])

>>> mysum([1, 2, 3, 4, 5])

15

OOPs

Python OOP is easy and simple

Class classname:

Def name():

Objectsinstance=classname()

Note no new keyword

first_class.py

Isinstance()

issubclass()

Inbuilt functions

hasattr(obj,attr)

getattr(obj,attr)=>retrieves attr value

setattr(obj,attr,val)=>set attr value

delattr(obj,attr)

first_class.py

add_book.py

More Resources

http://wiki.python.org/moin/BeginnersGuide

http://www.python.org/doc/faq/

Learn Python in 10 minutes: http://www.poromenos.org/tutorials/python

Byte of Python: http://www.swaroopch.com/notes/Python

Dive Into Python: http://diveintopython.org/

Google

Write most useful links for beginners starting

Any Questions ???

Write something more interactive

Thank You