Why isalnum() didn't output False when I use punctuations, spaces, etc in input?

[murmurgeneral]

isalnum() does return False for spaces.

for letter in "aA1 :/":
    print(letter, letter.isalnum())

Output:
a True
A True
1 True
  False
: False
/ False

Your problem must be something else.

You use slices, but you don't use them effectively. For example, this:

for i in s[0:2]:
    if i.isnumeric():
        return False

Could be written like this:

if any(c.isnumeric() for c in s[:2]
    return False

Or better yet

if not s[:2].isalpha():
    return False

Similarly, this loop should be removed:

for k in s:
    if k.isalphanum():
        ...
    else:
        return False

And replaced withL

if not s.isalnum():
    return False

Your program is also difficult to read because there is so much distance between a test and the function returning a False result because of the test, It would be easier to read if written like this:

pseudo code

def valid_plate(plate):
    if length of plate not valid:
        return False
    if all characters are not alphanumeric:
        return False
    if the first two characters are not alphabetic:
        return False
    if the first number is "0":
        return False
    if any charcter following the first number is not a number
        return False
    return True  # plate passed all the tests.

I appreciate you sharing this information. I find it handy.
boxing random