bytes.islower()

bytes.islower() bytearray.islower()

Return true if there is at least one lowercase ASCII character in the sequence and no uppercase ASCII characters, false otherwise.

For example:

>>> b'hello world'.islower()
True
>>> b'Hello world'.islower()
False

Lowercase ASCII characters are those byte values in the sequence b'abcdefghijklmnopqrstuvwxyz'. Uppercase ASCII characters are those byte values in the sequence b'ABCDEFGHIJKLMNOPQRSTUVWXYZ'.