[Python] Vanity Plates - Python

Trying to solve the questions of CS50 Python course.

Stuck at one of the questions: https://cs50.harvard.edu/python/2022/psets/2/plates/

Solved everything, however the "no letter after numeral" part is very hard for me.

I cannot understand why my solution does not work. Any idea?

Please do not give different solution, I read several of them, I want to understand where is the error in my version.

def main():
plate = input("Plate: ").strip()
if is_valid(plate):
print("Valid")
else:
print("Invalid")

def is_valid(s):
# check for non-letters and non-numbers
if not s.isalnum():
return False
# check for correct length
if len(s) < 2 or len(s) > 6:
return False
# check for correct first two characters
if s[0].isdigit() or s[1].isdigit():
return False
# check for incorrect third character if there is any
if len(s) > 2 and s[2] == "0":
return False
# check for errors in 4, 5, 6 length plate nemes:
# 1. no first numeral with "0" value
i = 0
while i < len(s):
if s.isdigit():
if s == "0":
return False
else:
break
i += 1
# 2. no letter after numeral
for i in range(len(s)):
if s.isdigit():
if i < len(s)-1 and s[i+1:].isalpha():
return False
# all possible errors checked
return True

main()


It seems the s[i+1:].isalpha() part never executes.

Continue reading...