[Python] Why Python's `all` built-in function returns `True` when checking if an empty string...

I wrote a function that checks if every character on a given string is also present in an arbitrary list. The code works for most cases, but when the input is an empty string, the built-in function all evaluates to True, even though that value isn't present at the ITEMS list:

ITEMS = ['a', 'b', 'c', 'd']

def check_all_chars_are_in_list(string):
return all(char in ITEMS for char in string)


if __name__ == "__main__":
print(check_all_chars_are_in_list('saban')) # False, as expected. (1)
print(check_all_chars_are_in_list('abcd')) # True, as expected. (2)
print(check_all_chars_are_in_list('')) # True (why?). (3)



I performed a manual test as to try and understand that behavior. I simply checked the in assertion via the terminal:

>>> st = ''
>>> l = ['a', 'b', 'c', 'd']
>>> st in l
False # As expected


But I got the expected False value, so how come the example (3) on my code evaluates to True? Can someone explain that to me, please?

Thank you!

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