Lesson1 python an introduction

Python – An Introduction Arulalan.T arulalant@gmail.com Centre for Atmospheric Sciences Indian Institute of Technology Delhi

Python is a Programming Language

There are so many Programming Languages. Why Python ?

Python is simple and beautiful

Python is Free Open Source Software

Can Do ● Text Handling ● Games ● System Administration ● NLP ● GUI programming ● Web Applications ● ... ● Database Apps ● Scientific Applications

Guido van Rossum Father of Python 1991

Perl Java Python Ruby PHP 1987 1991 1993 1995

Python is... A dynamic,open source programming language with a focus on simplicity and productivity. It has an elegant syntax that is natural to read and easy to write.

Quick and Easy Intrepreted Scripting Language Variable declarations are unnecessary Variables are not typed Syntax is simple and consistent Memory management is automatic

Object Oriented Programming Classes Methods Inheritance Modules etc.,

print “Hello World”

You have to follow the Indentation Correctly. Otherwise, Python will beat you !

Discipline Makes Good

Variables colored_index_cards

No Need to Declare Variable Types ! Python Knows Everything !

value = 10 print value value = 100.50 print value value = “This is String” print value * 3

name = raw_input(“What is Your name?”) print "Hello" , name , "Welcome"

if score >= 5000 : print “You win!” elif score <= 0 : print “Game over.” else: print “Current score:”,score print “Donen”

for i in range(1, 5): print i else: print 'The for loop is over'

number = 23 while True : guess = int(raw_input('Enter an integer : ')) if guess == number : print 'Congratulations, you guessed it.' running = False elif guess < number : print 'No, it is a little higher than that.' else: print 'No, it is a little lower than that.' print 'Done'

List = Array numbers = [ "zero", "one", "two", "three", "FOUR" ]

List = Array numbers = [ "zero", "one", "two", "three", "FOUR" ] numbers[0] >>> zero numbers[4] numbers[1] >>> FOUR >>> FOUR numbers[2] >>> three

Multi Dimension List numbers = [ ["zero", "one"],["two", "three", "FOUR" ]] numbers[0] >>> ["zero", "one"] numbers[0][0] numbers[1][1] >>> zero >>> FOUR len(numbers) >>> 2

Sort List primes = [ 11, 5, 7, 2, 13, 3 ]

Sort List primes = [ 11, 5, 7, 2, 13, 3 ] primes.sort()

Sort List primes = [ 11, 5, 7, 2, 13, 3 ] primes.sort() >>> [2, 3, 5, 7, 11, 13]

Sort List names = [ "Shrini", "Bala", "Suresh", "Arul"] names.sort() >>> ["Arul", "Bala","Shrini","Suresh"] names.reverse() >>> ["Suresh","Shrini","Bala","Arul"]

Mixed List names = [ "Shrini", 10, "Arul", 75.54] names[1]+10 >>> 20 names[2].upper() >>> ARUL

Append on List numbers = [ 1,3,5,7] numbers.append(9) >>> [1,3,5,7,9]

names = ('Arul','Dhastha','Raj') name.append('Selva') Error : Can not modify the tuple Tuple is immutable type

name = 'Arul' name[0] >>>'A' myname = 'Arul' + 'alan' >>> 'Arulalan'

split name = 'This is python string' name.split(' ') >>>['This','is','python','string'] comma = 'Shrini,Arul,Suresh' comma.split(',') >>> ['Shrini','Arul','Suresh']

join li = ['a','b','c','d'] s = '' new = s.join(li) >>> abcd new.split('') >>>['a','b','c','d']

'small'.upper() >>>'SMALL' 'BIG'.lower() >>> 'big' 'mIxEd'.swapcase() >>>'MiXwD'

menu = { “idly” : 2.50, “dosai” : 10.00, “coffee” : 5.00, “ice_cream” : 5.00, 100 : “Hundred” } menu[“idly”] 2.50 menu[100] Hundred

def sayHello(): print 'Hello World!' # block belonging of fn # End of function sayHello() # call the function

def printMax(a, b): if a > b: print a, 'is maximum' else: print b, 'is maximum' printMax(3, 4)

#!/usr/bin/python # Filename: using_sys.py import time print 'The sleep started' time.sleep(3) print 'The sleep finished'

#!/usr/bin/python import os os.listdir('/home/arulalan') os.walk('/home/arulalan')

#!/usr/bin/python # Filename: mymodule.py def sayhi(): print “Hi, this is mymodule speaking.” version = '0.1' # End of mymodule.py

#!/usr/bin/python # Filename: mymodule_demo.py import mymodule mymodule.sayhi() print 'Version', mymodule.version

#!/usr/bin/python # Filename: mymodule_demo2.py from mymodule import sayhi, version # Alternative: # from mymodule import * sayhi() print 'Version', version

Classes class Person: pass # An empty block p = Person() print p

Classes class Person: def sayHi(self): print 'Hello, how are you?' p = Person() p.sayHi()

Classes class Person: def __init__(self, name): #like contstructor self.name = name def sayHi(self): print 'Hello, my name is', self.name p = Person('Arulalan.T') p.sayHi()

Classes class A: def hello(self): print ' I am super class ' class B(A): def bye(self): print ' I am sub class ' p = B() p.hello() p.bye()

Classes class A: Var = 10 def __init__(self): self.public = 100 self._protected_ = 'protected' self.__private__ = 'private' Class B(A): pass p = B() p.__protected__

poem = ''' Programming is fun When the work is done if you wanna make your work also fun: use Python! ''' f = file('poem.txt', 'w') # open for 'w'riting f.write(poem) # write text to file f.close()

f= file('poem.txt','r') for line in f.readlines(): print line f.close()

import psycopg2 conn = psycopg2.connect(" dbname='pg_database' user='dbuser' host='localhost' password='dbpass' ") cur = conn.cursor() cur.execute("""SELECT * from pg_table""") rows = cur.fetchall() print rows cur.close() conn.close()

import psycopg2 conn = psycopg2.connect(" dbname='pg_database' user='dbuser' host='localhost' password='dbpass' ") cur = conn.cursor() cur.execute("'insert into pg_table values(1,'python')"') conn.commit() cur.close() conn.close()

Python – Shell Interactive Python ● ● Instance Responce ● Learn as you type

bpython ipython } teach you very easily

Python can communicate With Other Languages

Glade + Python + GTK = GUI APP

Lesson1 python an introduction

Lesson1 python an introduction

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