Python Extras

Introduction to Data Types in Python

Every value in Python has a datatype. Since everything is an object in Python programming, data types are actually classes and variables are instance (object) of these classes.

There are various data types in Python. Some of the important types are listed below.

Strings in Python

A string is a sequence of characters. It can be declared in python by using double quotes. Strings are immutable, i.e., they cannot be changed.

# Assigning string to a variable 
a = "This is a string"
print a 

Lists in Python

Lists are one of the most powerful tools in python. They are just like the arrays declared in other languages. But the most powerful thing is that list need not be always homogenous. A single list can contain strings, integers, as well as objects. Lists can also be used for implementing stacks and queues. Lists are mutable, i.e., they can be altered once declared.

# Declaring a list 
L = [1, "a" , "string" , 1+2] 
print L 
print L 
print L 
print L[1] 

The output is :

[1, 'a', 'string', 3]
[1, 'a', 'string', 3, 6]
[1, 'a', 'string', 3]

Tuples in Python

A tuple is a sequence of immutable Python objects. Tuples are just like lists with the exception that tuples cannot be changed once declared. Tuples are usually faster than lists.

tup = (1, "a", "string", 1+2) 
print tup 
print tup[1] 

The output is :

(1, 'a', 'string', 3)

Iterations in Python

Iterations or looping can be performed in python by ‘for’ and ‘while’ loops. Apart from iterating upon a particular condition, we can also iterate on strings, lists, and tuples.

Example1: Iteration by while loop for a condition

i = 1
while (i < 10): 
	i += 1
	print i, 

The output is :

2 3 4 5 6 7 8 9 10

Example 2: Iteration by for loop on string

s = "Hello World"
for i in s : 
	print i 

The output is :


Example 3: Iteration by for loop on list

L = [1, 4, 5, 7, 8, 9] 
for i in L: 
	print i, 

The output is :

1 4 5 7 8 9

Example 4 : Iteration by for loop for range

for i in range(0, 10): 
	print i, 

The output is :

0 1 2 3 4 5 6 7 8 9

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