Getting substring in Python

Python provides basic string manipulation functions that can be used by programmers to perform a wide range of sub-string operations. Strings are one of the most commonly used data types in Python, and understanding how to extract sub-strings from them is a key aspect of working with strings. In this tutorial, we will explore various methods of extracting sub-strings from strings using Python. 

Different ways of getting sub-string in Python :

• In python we can get sub-strings from a string using different methods, these include :
  • Basic sub-string slicing
  • Negative index slicing
  • Using String Methods
  • Using the split() method
  • Using Regular Expressions

Basic sub-string slicing :

• We can use the slicing technique to get a sub-string from a string in python.
  • We can use square brackets  [ ]  and index numbers to access a sub-string of characters within a string.
  • Separate the start and end indices with a colon  :  to slice a part of the string.
• Code Sample : 

my_string = "Hello, Kolledge!"
substring = my_string[11:15]
print(substring)         
   
# Output
# edge


   

Negative index slicing:

• We can use negative index numbers to access characters from the end of the string.
• Code Sample : 

my_string = "Hello, Kolledge!"
substring = my_string[-9:-1]
print(substring)          
   
# Output
# Kolledge

   

Using String Methods:

• We can use string methods such as find(), index(), and count() to find a sub-string within a string.
• the start index and length of the sub-string are used to slice the original string.
• Code Sample : 

my_string = "Hello, Kolledge!"
start_index = my_string.find("Kolledge")
length = len("Kolledge")
substring = my_string[start_index:start_index+length]
print(substring)

# Output
# Kolledge

Split the Original String:

• We can use the  split()  method to separate the original string into an array of sub-strings.
• we can then access the desired sub-string by its index.
• Code Sample : 

my_string = "Hello, Kolledge!"
substrings = my_string.split(", ")
substring = substrings[1]
print(substring)           
   
# Output
# Kolledge!

   

Using Regular Expressions:

• We can use the regular expressions to search for a pattern within a string.
• We can use the  re.search()  method of  re  module for this purpose.
• Extract the matched sub-string using the  group()  method or by slicing the original string based on the match indices.
• Code Sample : 

import re

my_string = "Hello 123 Kolledge Scholars."
pattern = r"\d+ \w+ \w+\."
match = re.search(pattern, my_string)
substring = match.group()
print(substring)
  
# Output  
# 123 Kolledge Scholars.

Concatenating Sub-strings:

• We can use the concatenation operator to concatenate multiple sub-strings together into a final string.
• Code Sample : 

my_string = "Hello, Kolledge!"
substring1 = my_string[0:5]
substring2 = my_string[8:]
substring3 = "Python"
final_string = substring1 + " " + substring3
print(final_string)     

# Output
# Hello Python