Write a python program to check if the substring is present in a given string or not.

 def is_substring_present(main_string, sub_string):

    main_len = 0

    sub_len = 0

    # Calculate length manually

    for _ in main_string:

        main_len += 1

    for _ in sub_string:

        sub_len += 1

    # Check for substring match

    for i in range(main_len - sub_len + 1):

        match = True

        for j in range(sub_len):

            if main_string[i + j] != sub_string[j]:

                match = False

                break

        if match:

            return True

    return False

# Example usage

main = "Welcome to Python programming"

sub = "Python"

if is_substring_present(main, sub):

    print("Substring is present in the main string.")

else:

    print("Substring is not present in the main string.")

Output: