Strings

A string is usually a bit of text (sequence of characters). In Python we use " (double quotes) or ' (single quotes) to represent a string. In this guide we will see how to create, access, use and manipulate strings in Python programming language.

1. How to create a String in Python

There are several ways to create strings in Python.
1. We can use ' (single quotes), see the string str in the following code.
2. We can use " (double quotes), see the string str2 in the source code below.
3. Triple double quotes "''" and triple single quotes "' are used for creating multi-line strings in Python. See the strings str3 and str4 in the following example.

# lets see the ways to create strings in Python
str = 'noidatut'
print(str)

str2 = "noida"
print(str2)

# multi-line string
str3 = """Welcome to 
   noidatut.com"""
print(str3)

str4 = '''This is a tech 
   blog'''
print(str4)

str = "Kevin"

# displaying whole string
print(str)

# displaying first character of string
print(str[0])

# displaying third character of string
print(str[2])

# displaying the last character of the string
print(str[-1])

# displaying the second last char of string
print(str[-2])

Output:

Kevin
K
v
n
i

3. Python String Operations

Lets see the operations that can be performed on the strings.

Getting a substring in Python - Slicing operation

We can slice a string to get a substring out of it. To understand the concept of slicing we must understand the positive and negative indexes in Python (see the example above to understand this). Lets take a look at the few examples of slicing.

 
str = "Beginnersbook"

# displaying whole string
print("The original string is: ", str)

# slicing 10th to the last character
print("str[9:]: ", str[9:])

# slicing 3rd to 6th character
print("str[2:6]: ", str[2:6])

# slicing from start to the 9th character
print("str[:9]: ", str[:9])

# slicing from 10th to second last character
print("str[9:-1]: ", str[9:-1])

Output

 
The original string is:  Beginnersbook
str[9:]:  book
str[2:6]:  ginn
str[:9]:  Beginners
str[9:-1]:  boo

Concatenation of strings in Python

The + operator is used for string concatenation in Python. Lets take an example to understand this:

str1 = "One"
str2 = "Two"
str3 = "Three"

# Concatenation of three strings
print(str1 + str2 + str3)

OneTwoThree

Note: When + operator is used on numbers it adds them but when it used on strings it concatenates them. However if you try to use this between string and number then it will throw TypeError.

4. How to get a sublist in Python using slicing

For example:

s = "one"
n = 2
print(s+n)

Output

TypeError: must be str, not int

str = "ABC"

# repeating the string str by 3 times
print(str*3)

ABCABCABC

Python Membership Operators in Strings

in: This checks whether a string is present in another string or not. It returns true if the entire string is found else it returns false. not in: It works just opposite to what "in" operator does. It returns true if the string is not found in the specified string else it returns false.

str = "Welcome to noidatut.com"
str2 = "Welcome"
str3 = "noida"
str4 = "XYZ"

# str2 is in str? True
print(str2 in str)

# str3 is in str? False
print(str3 in str)

# str4 not in str? True
print(str4 not in str)

True
False
True

The relational operators works on strings based on the ASCII values of characters.
The ASCII value of a is 97, b is 98 and so on.
The ASCII value of A is 65, B is 66 and so on.

str = "ABC"
str2 = "aBC"
str3 = "XYZ"
str4 = "XYz"

# ASCII value of str2 is > str? True
print(str2 > str)

# ASCII value of str3 is > str4? False
print(str3 > str4)

True
False