Why does an empty list evaluate to False in Python?

Question

In this code below, a list is set as a flag for while loop and then the author iterates by calling pop() on the list, and this loop produces an output as long as the list is not empty.

unconfirmed_users = ['alice', 'brian', 'candace']
while unconfirmed_users:
    current_user = unconfirmed_users.pop()
    print("Verifying user: " + current_user.title())
    confirmed_users.append(current_user)

Output:

Verifying user: Candace
Verifying user: Brian
Verifying user: Alice

I know that in programming languages, constants are treated as having boolean value True. So, I concur that even objects are treated as constants in python, perhaps. However if that it the case, even an empty list is an object too and is constant. Why does that evaluate to False?

ls = []
if(not ls):
    print("empty list evaluates to False")

Output:

empty list evaluates to False

Does this answer your question? [How do I check if a list is empty?](https://stackoverflow.com/questions/53513/how-do-i-check-if-a-list-is-empty) — The Singularity, Oct 12 '21 at 08:51
You assert that `"constants are treated as having boolean value True"`. I would like to see some evidence of that. — quamrana, Oct 12 '21 at 08:52
@Luke yes the top answer provided [this link](https://docs.python.org/3/library/stdtypes.html#truth-value-testing) which answered my question — Shubham Agrawal, Oct 12 '21 at 09:05
@quamrana Is there anything wrong if I code if(4): print("Constant is True") and it outputs Constant is True? — Shubham Agrawal, Oct 12 '21 at 09:08
Ok, compare that to: `if 0: pass; else: print("Constant is False")`. — quamrana, Oct 12 '21 at 09:10
Being a constant is nothing to do with being truthy. False is a constant. — khelwood, Oct 12 '21 at 10:04

Why does an empty list evaluate to False in Python?

0 Answers0