Why? not x means x is None or len(x) == 0 for lists. len(x) == 0 will raise an exception if x is None. In most cases, the distinction between None and [] isn't important, and if it is, I'd expect separate checks for those (again, for explicitness) since you'd presumably handle each case differently.

In short:

if the distinction between None and [] is important, have separate checks
if not, not x should be your default, since that way it's a common pattern for all types

[–] muntedcrocodile@lemm.ee 0 points 11 months ago (1 children)

I try to avoid having the same variable with different types I find it is often the cause of difficult to debug bugs. I struggle to think of a case where u would be performing a check that could be an empty list or None where both are expected possible values.

[–] sugar_in_your_tea@sh.itjust.works 0 points 11 months ago* (last edited 11 months ago) (1 children)

Really? I get that all the time. I do web dev, and our APIs have a lot of optional fields.

[–] muntedcrocodile@lemm.ee 0 points 11 months ago (1 children)

I do web dev

Theirs ur problem.

But in all seriousness I think if u def some_func(*args, kwarg=[]) Is a more explicit form of def some_func(*args, kwarg=None)

[–] sugar_in_your_tea@sh.itjust.works 0 points 11 months ago* (last edited 11 months ago) (1 children)

def some_func(*args, kwarg=[])

Don't do this:

def fun(l=[]):
    l.append(len(l))
    return l

fun()  # [0]
fun()  # [0, 1]
fun(l=[])  # [0]
fun()  # [0, 1, 2]
fun(l=None)  # raise AttributeError or TypeError if len(l) comes first

This can be downright cryptic if you're passing things dynamically, such as:

def caller(*args, **kwargs):
    fun(*args, **kwargs)

It's much safer to do a simple check at the beginning:

if not l: 
    l = []

[–] muntedcrocodile@lemm.ee 0 points 11 months ago (1 children)

I like the exception being raised their is no reason I should be passing in None to the function it means I've fucked up the value of whatever I'm passing in at some point.

[–] logging_strict@programming.dev 0 points 11 months ago (1 children)

Oh no a stray None! Take cover ...

Robust codebase should never fail from a stray None

Chaos testing is specifically geared towards bullet proofing code against unexpected param types including None.

The only exception is for private support function for type specific checking functions. Where it's obviously only for one type ever.

We live in clownworld, i'm a clown and keep the company of shit throwing monkeys.

[–] muntedcrocodile@lemm.ee 0 points 11 months ago

Ur function args if fucked up should always throw an error that's the entire point of python type hints

[–] UndercoverUlrikHD@programming.dev 0 points 11 months ago (1 children)

I'd argue that if it's strict explicitness you want, python is the wrong language. if not var is a standard pattern in python. You would be making your code slower for no good reason.

[–] Ephera@lemmy.ml 0 points 11 months ago (1 children)

You always want explicitness when programming. Not everyone reading your code will be deep into Python and relying on falsiness makes it harder to understand.

[–] fruitcantfly@programming.dev 0 points 11 months ago (1 children)

Containers being "truthy" is quite basic Python and you will find this idiom used in nearly every Python code base in my experience

[–] Ephera@lemmy.ml 0 points 11 months ago* (last edited 11 months ago) (1 children)

Yeah, I'm talking less deep than that. Plenty programming beginners will be reading Python code. And personally, I'm a fulltime software engineer, but just don't do much Python, so while I had it in the back of my mind that Python does truthiness, I would have still thought that var must be a boolean, because it's being negated. Obviously, a different variable name might've given me more of a clue, but it really doesn't reduce mental complexity when I can't be sure what's actually in a variable.

[–] fruitcantfly@programming.dev 0 points 11 months ago* (last edited 11 months ago)

But if those beginners want to stop being beginners, then they must learn the basics of the language. It makes no more sense to demand that everyone who programs in Python caters to beginners, than it makes to demand that everyone writing in English write at a 3rd grade reading level for the sake of English language learners

[–] ExtremeDullard@lemmy.sdf.org 0 points 11 months ago* (last edited 11 months ago)

In complex cases where speed is less important than maintainability, I tend to agree.

In this case, a simple comment would suffice. And in fact nothing at all would be okay for any half-competent Python coder, as testing if lists are empty with if not is super-standard.