Avoiding "Too broad exception clause" warning in PyCharm

Question

I'm writing an exception clause at the top level of a script, and I just want it to log whatever errors occur. Annoyingly, PyCharm complains if I just catch Exception.

import logging

logging.basicConfig()

try:
    raise RuntimeError('Bad stuff happened.')
except Exception:  # <= causes warning: Too broad exception clause
    logging.error('Failed.', exc_info=True)

Is there something wrong with this handler? If not, how can I tell PyCharm to shut up about it?

Solution 1

From a comment by Joran: you can use # noinspection PyBroadException to tell PyCharm that you're OK with this exception clause. This is what I was originally looking for, but I missed the option to suppress the inspection in the suggestions menu.

import logging

logging.basicConfig()

# noinspection PyBroadException
try:
    raise RuntimeError('Bad stuff happened.')
except Exception:
    logging.error('Failed.', exc_info=True)

If you don't even want to log the exception, and you just want to suppress it without PyCharm complaining, there's a new feature in Python 3.4: contextlib.suppress().

import contextlib

with contextlib.suppress(Exception):
    raise RuntimeError('Bad stuff happened.')

That's equivalent to this:

try:
    raise RuntimeError('Bad stuff happened.')
except Exception:
    pass

Solution 2

I am reluctant to turn off warnings as a matter of principle.

In the case presented, you know well what the exception is. It might be best to just be specific. For example:

try:
    raise RuntimeError("Oops")
except RuntimeError as e:
    print(e, "was handled")

will yield "Oops was handled".

If there are a couple of possible exceptions, you could use two except clauses. If there could be a multitude of possible exceptions, should one attempt to use a single try-block to handle everything? It might be better to reconsider the design!

Solution 3

Not sure about your PyCharm version (mine is 2019.2), but I strongly recommend disabling this PyCharm inspection in File> Settings> Editor> Inspections and type "too broad". In Python tab, deselect "too broad exceptions clauses" to avoid those. I believe this way PyCharm would show you the correct expression inspection

Solution 4

I found a hint in this closed feature request for PyCharm:

I suggest you to mark this inspection as 'okay' if the except block makes use of exception instance e somehow.

Because I'm logging with exc_info=True, I'm implicitly using the current exception object, but PyCharm doesn't know that. To make it explicit, I can pass the exception object to exc_info. Since Python 3.5, the logger methods have accepted an exception instance to report, as well as accepting any truthy value to report the current exception and stack trace in the log.

import logging

logging.basicConfig()

try:
    raise RuntimeError('Bad stuff happened.')
except Exception as e:
    logging.error('Failed.', exc_info=e)

View more solutions

Comments

[user2357112]

That's going to be horribly misleading to anyone reading this code later.

[Joran Beasley]

you could also add # noinspection PyBroadException to right above the try: this would tell pycharm (and probably other IDE's that you know its too broad and you are ok with it)

[Sam Rockett]

Why wouldd this be horribly misleading? Looks like the logging module checks either isinstance(exc_info, BaseException) in which case it extracts the data from the exception, tuple in which case it assumes the exc_info is accurate, or truthy in which case it uses sys.exc_info(). Passing exc_info=True and exc_info=e should yield identical results, no? (logging.__init__ at line 1461)

[Don Kirkby]

Thanks, @Sam, I hadn't noticed that change to exc_info. I've updated the answer to explain it better.

[Matthias Luh]

Then again, there are cases where you do not know the errors in advance and still want to catch them. For example in the socket library: "In non-blocking mode, operations fail (with an error that is unfortunately system-dependent) if they cannot be completed immediately"

[Matthias Luh]

In PyCharm 2021.2.2 this option doesn't exist. I just realized "# noinspection PyBroadException" only helps if it is inserted right before each try statement