The doc of bytes.isalnum() and bytearray.isalnum() says alphabetical ASCII characters or ASCII decimal digits as shown below:

Return True if all bytes in the sequence are alphabetical ASCII characters or ASCII decimal digits and the sequence is not empty, False otherwise. Alphabetic ASCII characters are those byte values in the sequence ...

But bytes.isalnum() and bytearray.isalnum() work for alphabetical ASCII characters and/or ASCII decimal digits as shown below and actually, the word alphabetical which isn't proper should be replaced with alphabetic:

print(b'abc123'.isalnum())
print(b'abc'.isalnum())
print(b'123'.isalnum())
print(bytearray(b'abc123').isalnum())
print(bytearray(b'abc').isalnum())
print(bytearray(b'123').isalnum())
# True

print(b'a b c 1 2 3'.isalnum())
print(b'a b c'.isalnum())
print(b'1 2 3'.isalnum())
print(bytearray(b'a b c 1 2 3').isalnum())
print(bytearray(b'a b c').isalnum())
print(bytearray(b'1 2 3').isalnum())
# False

So, the doc of bytes.isalnum() and bytearray.isalnum() should say alphabetic ASCII characters and/or ASCII decimal digits as shown below:

Return True if all bytes in the sequence are alphabetic ASCII characters and/or ASCII decimal digits and the sequence is not empty, False otherwise. Alphabetic ASCII characters are those byte values in the sequence ...

Linked PRs

• gh-137267: Clarify bytes.isalnum and bytearray.isalnum doc wording #137269