Meme is funny, but that exception used as flow control hurts.
Tbf python guidelines encourage it over if/else in cases like this. “Easier to ask for forgiveness than for permission” or something along the lines
Day 598 of asking for a way to tell which functions throw exceptions in Python so I can know when to wrap in try catch. Seems to me that every other language has this, but when I’ve asked for at least a linter that can tell me I’m calling a function that throws, the general answer has been “why would you want that?”
How am I supposed to ask for forgiveness if it’s impossible to know that I’m doing something risky in the first place?
Yeah, for this reason I would pretty much never encourage exceptions in Python over some other form of error handling. It’s so frustrating when called code throws some random exceptions that are completely undocumented. This is one of the few things Java got (sort of) right
cant practically anything throw an exception given the right (sometimes extremely remotely possible) circumstances?
Is this feature common in scripting/interpreted languages? Feels like those two things don’t work together.
python guidelines
Do you have a specific PEP you’re referencing or is this one of those “I assume this must be the case because of how common using try/except statements for flow control are” kind of things?
Pretty sure its not a PEP, but the python glossary mentions it. Searching ‘python EAFP’ brings up a lot of discussion on the topic too, so if nothing else its definitely a widespread phenomenon
Like most things in life, context matters. In the OP it seems like the check
function is used specifically so it could raise a PaymentException
if the payment hasn’t been received… That’s not a “forgiveness/permission” context, this is a yes or no question, hence should have been an if.
Still hurts, but sometimes it’s the only option.
If you’re trying to confirm things like account existence/deletion, there’s often no “account exists” function to return true or false. You just have to figure out the specific exception thrown and catch that specific one.
The worst are libraries that don’t give specific exceptions, so you have to catch all exceptions then do extra work to tell what the specific situation is. Does the account not exist, or is the system unreachable?
so you have to catch all exceptions then do extra work to tell what the specific situation is
That’s horrifying. That’s a solid reason to avoid Python like the plague.
While i also disagree with python’s tendency to use exceptions as control flow
Python is a pretty stellar scripting language. I wouldn’t use it for app dev, but it’s quite handy for the odd automation or CLI task
Yeah, I had a similar case with some authentication middleware I used that was part of a library.
It would always throw an exception when a user wasn’t authenticated instead of just giving me some flag I could check.
Wouldn’t have done it that way, but it was okay for an API controller.