python - Why does checking an empty string against string.hexdigits() return valid? -

i have 2 functions, 1 cleans input text, , 1 tests if cleantext hexadecimal. when passing cleaner function string of spaces, strips spaces, leaving null string.

what don't why string.hexdigits() doesn't barf on null string, , let's pass through valid hex.

def testhex(ciphertext):     cleancipher = cleanhex(ciphertext)     if all(h in string.hexdigits h in cleancipher):         print('string valid hex.')     else:         print('string not valid hex.')  def cleanhex(ciphertext):     return(ciphertext.replace(' ', '').replace('0x', '').replace(':', '').replace('\\x', '').strip()) 

testhex outputs string valid hex. empty strings because all returns true empty iterables

it documented

all(iterable)

return true if elements of iterable true (or if iterable empty).