How does the "all" function in Python work?

Question

I searched for understanding about the all function in Python, and I found this, according to here:

all will return True only when all the elements are Truthy.

But when I work with this function it's acting differently:

'?' == True   # False
'!' == True   # False
all(['?','!']) # True

Why is it that when all elements in input are False it returns True? Did I misunderstand its functionality or is there an explanation?

score 9 · Accepted Answer · answered Feb 28 '16 at 17:29

9

only when all the elements are Truthy.

Truthy != True.

all essentially checks whether bool(something) is True (for all somethings in the iterable).

>>> "?" == True
False
>>> "?" == False # it's not False either
False
>>> bool("?")
True

answered Feb 28 '16 at 17:29

L3viathan

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Only `bool("")` is False (in string) ? every non empty string is True? – ᴀʀᴍᴀɴ Feb 28 '16 at 17:32

score 1 · Answer 2 · answered Feb 28 '16 at 17:29

1

'?' and '!' are both truthy since they are non-empty Strings.

There's a difference between True and "truthy". Truthy means that when coerced, it can evaluate to True. That's different from it being == to True though.

answered Feb 28 '16 at 17:29

Carcigenicate

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Downvoter, please comment. I updated the second half of my answer since I misinterpreted him. – Carcigenicate Feb 28 '16 at 17:31

score -2 · Answer 3 · answered Apr 04 '17 at 11:30

-2

all() function is used when we want to check that if all the items in a list are iterable or not. For ex : x=[1,2,3,4,5] all(x) It will return True.

answered Apr 04 '17 at 11:30

Vibhu Pandey

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How does the "all" function in Python work?

3 Answers3