Solution Exercise 67: python algorithm to check if a given string start with an other string

Exercise 67

Write a Python program as function that checks whether a given string 's' starts with another string 's1', without using the built-in startswith() method.

Solution

def starts_with(s: str, s1: str) -> bool:
    """
    checks if s is at least as long as s1, and if not, 
    it immediately returns False since s1 cannot be a prefix of s
    """
    if len(s1) > len(s):
        return False

    """
    Next, it iterates through the characters of s1 using a loop and compares them 
    to the corresponding characters in s. If any of these characters differ, 
    the function returns False, indicating that s does not start with s1.
    """
    for i in range(len(s1)):
        if s[i] != s1[i]:
            return False
    return True
# Example of use of this function
s = "Python Programmin"
s1 = "Pyth"
print(starts_with(s, s1))  # Output: True

s2 = "Java"
print(starts_with(s, s2))  # Output: False

Younes Derfoufi
my-courses.net