def capitalize_first_letter(s):
    """Capitalize (only) the first character of a string

    This is an alternative to the  built-in str function capitalize()
    which changes all letters following the first to lower case.

    Args:
        s (str): the string to be capitalized.

    Returns:
        (str): the modified string
    """
    base = []
    if len(s) > 0:
        base += s[0].upper()
    if len(s) > 1:
        base += s[1:]
    return ''.join(base)