Welcome back to another coding exercise solution!

This is my solution to the coding exercise. Again, it may be slightly different from yours!

import re


def is_filename_safe(filename):
    regex = '^[a-zA-Z0-9][a-zA-Z0-9_()-]*(\.jpg|\.jpeg|\.png|\.gif)$'
    # ^[a-zA-Z0-9]      start with a-zA-Z0-9
    # [a-zA-Z0-9_()-]+      then only contains a-zA-Z0-9_()- for any number of times
    # (\.jpg|\.jpeg|\.png|\.gif)$       at last, it must end with one of the four extensions, remember to escape the dot
    # since we check from start to end, it can either match the whole string or none
    return re.match(regex, filename) is not None

Let me know how you got on!

Kind regards,

— Jose and the Teclado team