🔒 exception handling

[native musk]

I need someone to explain exception handling

[old stone]

@native musk

Python help channel opened

Remember to:

• Ask your Python question, not if you can ask or if there's an expert who can help.
• Show a code sample as text (rather than a screenshot) and the error message, if you've got one.
• Explain what you expect to happen and what actually happens.

:warning: Do not pip install anything that isn't related to your question, especially if asked to over DMs.

Closes after a period of inactivity, or when you send !close.

[quick acorn]

Have you got a specific question, or some example?

It's not complex, but hard to succinctly describe.

[native musk]

not really it may be about anything in the exam so what I'm facing is i dont understand it that much

[quick acorn]

Ok.

Python "raises" an exception when something goes wrong. This might be a call which failed like open("nonexistent-filename") or an invalid value for a function call like int("not an integer!").

This has 2 main features:

• you can, loosely, write code as if it will work and rely on it raising an exception for bad situations - this avoids a lot of if-statements like if "abc".find("def") == -1: # "def" wasn't there - statements whose purpose os to "check" for failure
• you can decide where to handle to problem - sometimes (often!) it's not something to fix where it happened because the "fix" depends on some larger context

A try/except statement is for catching raised exceptions:

try:
    with open("nonexistent-filename") as f:
        ... process the data in the file ...
except FileNotFoundException:
    # handle the file not being there
    data = [] # no data, but ok!

Generally:

• you want the try/except around the smallest piece of code possible, so that you know what raised the exception
• you want to catch only things for which you have a well defined recovery action - in the above, we consider a missing file to be ok, we will pretend like it was empty
• you don't catch other things, so that they can bubble out and be debugged

That last is: suppose we got an exception because we do not have read permission on the file. We do not catch that because that isn't something we should paper over and ignore. Probably it means we're trying to work on data we shoud not have access to or the outer environment is badly set up. Either way, we don't catch it.

That's most of it. There's a heap of details, but that's the core stuff.

Questions?

[native musk]

no thank you

thanks man @quick acorn 🌹

[quick acorn]

Glad to be of service.

[old stone]

Python help channel closed for inactivity

This help channel has been closed. Feel free to create a new post in #1035199133436354600. To maximize your chances of getting a response, check out this guide on asking good questions.