this post was submitted on 17 Apr 2025
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[–] LostXOR@fedia.io 23 points 4 days ago (4 children)

I think it's because not() is equivalent to not(None), and since None is falsy not(None) returns True.

[–] takeda@lemm.ee 6 points 4 days ago (1 children)

Are you sure?

I can't test it now, but to me it looks like () is an empty tuple. Python behavior is that for logic operations empty set equals to false. Then we apply not to get True. Not having space between not operator and parentheses makes it look like it is a function.

[–] LostXOR@fedia.io 1 points 4 days ago

I'm pretty sure you're right; that makes more sense.

[–] Ziglin@lemmy.world 5 points 4 days ago (1 children)

Why is literally nothing equivalent to None? Is it because None is the default value of an optional parameter? (If so why oh why is it optional)

[–] spooky2092@lemmy.blahaj.zone 5 points 4 days ago* (last edited 4 days ago) (1 children)

Because nothing isn't something, and something is true. It's base Boolean logic where everything is either true or false. Null/nothing is false.

It's a weird way to think about conditionals, but it makes sense when you use them in real examples. In my case, I use them like this when I need to make sure that a variable has a value. So I can do something like

If(variable){do things with the variable}else{do stuff when the variable doesn't exist}

[–] Ziglin@lemmy.world 1 points 4 days ago (2 children)

I understand that, it makes sense. But why does it not throw an error? The parameter is missing after all.

[–] takeda@lemm.ee 2 points 3 days ago (1 children)

Actually the explanation is wrong.

not()

is actually

not ()

not is a keyword not a function.

Boolean of empty tuple is False and then not negates it.

I explained it better here:

https://lemm.ee/post/61594443/19783421

[–] Ziglin@lemmy.world 1 points 3 days ago

That makes a lot more sense, thanks I did see in the syntax highlighting that it was a keyword but forgot that none of them took parameters.

[–] spooky2092@lemmy.blahaj.zone 0 points 4 days ago

No it's not, "" (a null/empty string) is the parameter. Not every function needs a parameter to be valid, and negation is one of them. Negating nothing is something, so "not()" = "not(null)" = "not(false)" = "true"

[–] brb@sh.itjust.works 5 points 4 days ago

God I love python

[–] humanspiral@lemmy.ca 2 points 4 days ago (1 children)

in J, many other languages, not null is null.

[–] pupbiru@aussie.zone 3 points 4 days ago
a  = null
if not a:
   …

if not a were null then an if that evaluates that would evaluate it as falsy… also if a would evaluate as falsy :/ that’s far weirder behaviour