Requiring a regex and moving to 6 kyu would be more appropriate for Python.

Python: missing

from solution import alphanumeric
import codewars_test as test

in the sample tests and full tests

there is actually an issue here. since Codewars moved away from concatenating the user's solution and the tests for Python, whatever renaming and imports the user makes should stay contained within the solution module. however, because the Python tests suite does not explicitely import the user's function in this kata, Codewars inserts from solution import * to the tests for backwards-compatibility. alphanumeric should be imported explicitely instead; raising an issue about that

the reason your code fails is because you overwrite str in your import line

this means str is no longer what it should be in the Python code,
and so that breaks the tester

this is why you should never overwrite a built-in function, a module name, or a keyword, et cetera

first, you should use a spoiler flag if you post code

I added the flag to your comment

Suggest adding test cases for the literal strings "null", "nil", "none", etc; I see at least one solution that improperly returns that these are not alphanumeric (they are)

Rust's test and attempt give error: unresolved import super::alphanumeric

solution in 1 string :0

I appreciate your response a lot! Thanks!

• forbidding things is very hard in Python; the language is very dynamic and there are many, many ways to bypass naive restrictions
• this kata is old (more than 11 years old...) and overranked. there has been a rank deflation on Codewars over time, and unfortunately ranks cannot be changed
• in any case, this is not a proper kata issue

It's more like a 7 kyu.

Much too easy for 5 kyu!

Why should they be false?