Python Program to check if a string starts with a substring using regex

When it is required to check if a string starts with a specific substring or not, with the help of regular expression, a method is defined that iterates through the string and uses the ‘search’ method to check if a string begins with a specific substring or not.

Example

Below is a demonstration of the same

import re

def check_string(my_string, sub_string) :

   if (sub_string in my_string):

      concat_string = "^" + sub_string
      result = re.search(concat_string, my_string)

      if result :
         print("The string starts with the given substring")
      else :
         print("The string doesnot start with the given substring")

   else :
      print("It is not a substring")

my_string = "Python coding is fun to learn"
sub_string = "Python"

print("The string is :")
print(my_string)

print("The sub-string is :")
print(sub_string)

check_string(my_string, sub_string)

Output

The string is :
Python coding is fun to learn
The sub-string is :
Python
The string starts with the given substring

Explanation

• The required packages are imported.

• A method named ‘check_string’ is defined that takes the string and a substring as parameter.

• It iterates through the string, and concatenates the ‘^’ with the substring.

• This is assigned to a new variable.

• The ‘search’ method is used to check for the substring in the new variable.

• The result is assigned to a variable.

• If this is result is a true value, relevant output is displayed on the console.

• Outside the console, a string is defined, and is displayed on the console.

• A substring is defined and is displayed on the console.

• The method is called by passing the string and the substring.

• The output is displayed on the console.