how to check if a string is in a file python

1def search_string_in_file(file_name, string_to_search):
2    """Search for the given string in file and return lines containing that string,
3    along with line numbers"""
4    line_number = 0
5    list_of_results = []
6    # Open the file in read only mode
7    with open(file_name, 'r') as read_obj:
8        # Read all lines in the file one by one
9        for line in read_obj:
10            # For each line, check if line contains the string
11            line_number += 1
12            if string_to_search in line:
13                # If yes, then add the line number & line as a tuple in the list
14                list_of_results.append((line_number, line.rstrip()))
15 
16    # Return list of tuples containing line numbers and lines where string is found
17    return list_of_results
18