# python2
import os
import string

charset = string.ascii_uppercase + string.digits
random_bytes = os.urandom(25)
len_charset = len(charset)
indices = [int(len_charset * (ord(byte) / 256.0)) for byte in random_bytes]
defaultToken = "".join([charset[index] for index in indices])

# python3
"".join(secrets.choice(string.ascii_uppercase + string.digits) for i in range(25))