A rough presentation on the basics of Python, which I gave to my team at SocialTwist.

1. Introduction to Python
Abhinav Upadhyay
<abhinav@socialtwist.com>

2. What is Python
● A dynamically typed, object oriented
programmnig language
● Created by Guido van Rossum in 1989

3. Features
● High-level
● Object Oriented
● Scalable
● Extensible
● Portable
● Readable
● Managed runtime
● Interpreted and Byte-compiled.

4. Difference from C Style Languages
● Forget ; and {}
● Embrace indentation

5. Getting Started
● “Hello, World” in Python:
print 'Hello, world!'

6. Getting Started
● Redirecting your output
file = open('output', 'w')
print >> file, 'Hello, world!'

7. Making your program interactive
● Getting user input:
name = raw_input('Enter your name: ')
print name

8. Comments in Python
● Single line comments --> #
● Multiline comments --> ''' your comment '''
● Docstrings

9. Operators
● Numerical operators: +, -, /, //, *, **, %
● Comparision operators: <, >, <=, >=, ==, !=, <>
● Logical operators: and, or, not

10. Numerical types in Python
● int
– long
– float
● bool
● complex

11. String handling in Python
● Creating a string:
my_string = “this is a string”
my_2nd_string = 'string using single
quotes'
my_3rd_string = ''' triple quotes also
work'''

12. String handling in Python
● String operators:
+ --> Performs concatenation
str1 = 'a'
str2 = 'b'
print a + b
Output: 'ab'
* --> Performs repitition
str1 = 'a'
print a * 5
Output: 'aaaaa'

13. String handling in Python
● String operators:
% --> Format operator
age = 20
str1 = 'Your age is %dn' % age
Output: 'Your age is 20'

14. String handling in Python
● String Manipulation:
– Indices starting from 0
– Indices from last element starting with -1
str1 = 'hello, world'
print str1[0]
Output: 'h'
print str[-1]
Output: 'd'
Print str[-2]
Output: 'l'

15. String handling in Python
Slicing:
● Use the slicing operator [] to slice the string into smaller
parts
● Syntax: str[m:n]
– This will print the characters of the string starting from the mth position till
the nth position (but excluding the nth character)
str1 = '0123456789'
print str1[1:4]
Output: 123

16. Built-in functions of Python
● Functions which are built-in to the Python
interpreter and are always available
● Examples: pow(), print(), open(), int(), str(),
etc.
● Some useful BIFs:
– type(), help(), dir()

17. Common Python Data-Structures
● Lists:
– Array like data-structure
– Objects stored in sequential order
– Indices starting from 0
– Can store arbitrary number of objects (unlike fixed
length arrays in other languages)
– Can also store objects of different types in the
same list.

18. Common Python Data-Structures
● Tuples:
– Similar to lists, with two visible differences:
● Lists use [], while tuples use () in their syntax
● Tuples are immutable data-structures

19. Common Python Data-Structures
● Dictionaries:
– Hash tables
– Can store any number of objects
– {} are used for creating dictionaries

20. Loops in Python
● For loop:
Used for iterating over a sequence of items
for item in list:
print item

21. Loops in Python
● While loop:
Used for executing a suite of code a number
of times.
Count = 0
while count < 10:
print count
count += 1

22. Conditionals
● If-elif-else
if <condition>:
#statement1
#statement2
elif <condition 2>:
#statement3
#statement4
else:
pass

23. File handling
F = open('file1.txt', 'r')
for eachLine in F:
print F
F.close()
f = open('file2.txt', 'w')
f.write('hello, worldn')
f.close()

24. Functions in Python
● The 'def' keyword
● The return value
● Returning multiple values