This is an introduction to basic Python constructs just to initiate executing Python code in minutes

1. An Introduction to Python
SNAKES ON THE WEB:- Python
Sumit Kumar Raj

2. Contents
● What is Python ???
● Why Python ???
● Who uses Python ???
● Running Python
● Syntax Walkthroughs
● Python Twitter API
● Coding Mantras

3. What is Python ???
 General purpose, object-oriented, high level
programming language
 Widely used in the industry
 Used in web programming and in standalone
applications

4. 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 Dropbox

5. Why Python ???
● Readability, maintainability, very clear readable syntax
● Fast development and all just works the first time...
● very high level dynamic data types
● Automatic memory management
● Free and open source
● Implemented under an open source license. Freely usable
and distributable, even for commercial use.
● Simplicity, Availability (cross-platform), Interactivity (interpreted
language)
● Get a good salaried Job

6. Batteries Included
● The Python standard library is very extensive
● regular expressions, codecs
● date and time, collections, theads 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 ...

7. Who uses Python ???

8. Hello World
In addition to being a programming language, Python is also an
interpreter. The interpreter reads other Python programs and
commands, and executes them
Lets write our first Python Program
print “Hello World!”

9. Python is simple
print "Hello World!" Python
#include <iostream.h>
C++
int main()
{
cout << "Hello World!";
}
public class helloWorld
{
public static void main(String [] args) Java
{
System.out.println("Hello World!");
}
}

10. Let's dive into some code
Variables and types
>>> a = 'Hello world!' # this is an assignment statement
>>> print a
'Hello world!'
>>> type(a) # expression: outputs the value in interactive mode
<type 'str'>
• Variables are created when they are assigned
• No declaration required
• The variable name is case sensitive: ‘val’ is not the same as ‘Val’
• The type of the variable is determined by Python
• A variable can be reassigned to whatever, whenever
>>> n = 12 >>> n = 'apa'
>>> print n >>> print n
12 'apa'
>>> type(n) >>> type(n)
<type 'int'> <type 'str'>
>>> n = 12.0
>>> type(n)
<type 'float'>

11. Strings: format()
>>>age = 22
>>>name = 'Sumit'
>>>len(name)
>>>print “I am %s and I have owned %d cars” %(“sumit”, 3)
I am sumit I have owned 3 cars
>>> name = name + ”Raj”
>>> 3*name
>>>name[:]

12. Do it !
 Write a Python program to assign your USN
and Name to variables and print them.
 Print your name and house number using
print formatting string “I am %s, and my
house address number is %d” and a tuple

13. Strings...
>>> string.lower()
>>> string.upper()
>>> string[start:end:stride]
>>> S = ‘hello world’
>>> S[0] = ‘h’
>>> S[1] = ‘e’
>>> S[-1] = ‘d’
>>> S[1:3] = ‘el’
>>> S[:-2] = ‘hello wor’
>>> S[2:] = ‘llo world’

14. Do it...
1) Create a variable that has your first and last name
2) Print out the first letter of your first name
3) Using splicing, extract your last name from the variable and
assign it to another
4) Try to set the first letter of your name to lowercase - what
happens? Why?
5) Have Python print out the length of your name string, hint
use len()

15. Indentation
● Python uses whitespace to determine blocks of code
def greet(person):
if person == “Tim”:
print (“Hello Master”)
else:
print (“Hello {name}”.format(name=person))

16. Control Flow
if guess == number: while True:
#do something #do something
#break when done
elif guess < number: break
else:
#do something else
#do something when the loop ends
else:
#do something else
for i in range(1, 5): for i in range(1, 5,2):
print(i) print(i)
else: else:
print('The for loop is over') print('The for loop is over')
#1,2,3,4 #1,3

17. Data Structures
● List
● Mutable data type, array-like
● [1, 2, 4, “Hello”, False]
● list.sort() ,list.append() ,len(list), list[i]
● Tuple
● Immutable data type, faster than lists
● (1, 2, 3, “Hello”, False)
● Dictionary
● {42: “The answer”, “key”: “value”}

18. Functions
def sayHello():
print('Hello World!')
● Order is important unless using the name
def foo(name, age, address) :
pass
foo('Tim', address='Home', age=36)
● Default arguments are supported
def greet(name='World')

19. 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 y
printMax(3, 5)

20. Input & Output
#input
something = input('Enter text: ')
#output
print(something)

21. Files
myString = ”This is a test string”
f = open('test.txt', 'w') # open for 'w'riting
f.write(myString) # write text to file
f.close() # close the file
f = open('test.txt') #read mode
while True:
line = f.readline()
if len(line) == 0: # Zero length indicates EOF
break
print(line, end='')
f.close() # close the file

22. Linux and Python
”Talk is cheap. Show me the code.”
Linus Torvalds

23. A small code to get tweets ...
from twython import Twython
twitter = Twython()
# First, let's grab a user's timeline. Use the 'screen_name'
parameter with a Twitter user name.
user_timeline =
twitter.getUserTimeline(screen_name="sumit12dec",)
#count=100, include_rts=1
for tweet in user_timeline:
print tweet["text"]

24. More Resources
● http://www.python.org/doc/faq/
● http://www.codecademy.com/tracks/python
● http://codingbat.com/python
● http://www.tutorialspoint.com/python/index.htm
● How to Think Like a Computer Scientist, Learning with Python
Allen Downey, Jeffrey Elkner, Chris Meyers
● Google

25. Coding Mantras
 InterviewStreet
 ProjectEuler
 GSoC
 BangPypers
 Open Source Projects

26. Any Questions ???

27. Thank You
Reach me @:
facebook.com/sumit12dec
sumit786raj@gmail.com
9590 285 524