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78 points

Meme is funny, but that exception used as flow control hurts.

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39 points

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

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33 points

pythonic != good

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7 points

Truers, just mentioning it

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21 points

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?

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8 points

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

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Deleted by creator
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2 points

cant practically anything throw an exception given the right (sometimes extremely remotely possible) circumstances?

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1 point

Is this feature common in scripting/interpreted languages? Feels like those two things don’t work together.

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0 points

Check out Rust

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10 points

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?

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4 points

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

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3 points

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.

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11 points

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?

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3 points

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.

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4 points

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

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3 points

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.

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2 points

nothing wrong with that - it is an exception, as in, the customer is likely lost after that anyway.

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