Prerequisite: Regular Expression in Python
Given a string str, the task is to check if a string starts with a given substring or not using regular expression.
Examples:
Input: String: "geeks for geeks makes learning fun" Substring: "geeks" Output: True Input: String: "geeks for geeks makes learning fun" Substring: "makes" Output: False
Approach 1:
Here, we first check a given substring present in a string or not if yes then we use search() function of re library along with metacharacter “^”. This metacharacter checks for a given string starts with substring provided or not.
Below is the implementation of the above approach:
Python3
# import library import re # define a function def find(string, sample) : # check substring present # in a string or not if (sample in string): y = "^" + sample # check if string starts # with the substring x = re.search(y, string) if x : print ( "string starts with the given substring" ) else : print ( "string doesn't start with the given substring" ) else : print ( "entered string isn't a substring" ) # Driver code string = "geeks for geeks makes learning fun" sample = "geeks" # function call find(string, sample) sample = "makes" # function call find(string, sample) |
Output:
string starts with the given substring string doesn't start with the given substring
Approach 2:
Here, we first check a given substring present in a string or not if yes then we use search() function of re library along with metacharacter “\A”. This metacharacter checks for a given string starts with substring provided or not.
Below is the implementation of the above approach:
Python3
# import library import re # define a function def find(string, sample) : # check substring present # in a string or not if (sample in string): y = "\A" + sample # check if string starts # with the substring x = re.search(y, string) if x : print ( "string starts with the given substring" ) else : print ( "string doesn't start with the given substring" ) else : print ( "entered string isn't a substring" ) # Driver code string = "geeks for geeks makes learning fun" sample = "geeks" # function call find(string, sample) sample = "makes" # function call find(string, sample) |
Output:
string starts with the given substring string doesn't start with the given substring
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