Python: How to ignore an exception and proceed? [duplicate]

445

except:
    pass

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• except Exception: pass # important not to swallow other exceptions! - Roger Pate
• @Aaron - I agree, but the question wasn't if this was a good/bad idea - David
• This will catch SystemExit, KeyboardInterrupt and other things that you probably don't want to catch. - FogleBird
• It won't catch KeyboardInterrupt. For example: while True: try: f = open('filedoesnotexist.txt')` except: pass KeyboardInterrupt stops and exits the code. - Chthonic Project
• @ChthonicProject a bare except will catch any exception, including a KeyboardInterrupt, but only if it happens inside the try. In your example there, a KeyboardInterrupt can occur before the try or inside the except, where it won't be caught. If you run an example like while True: try: pass except: pass, you'll find that the KeyboardInterrupt gets caught just about 50% of the time. If you time.sleep(1) inside the try, you'll find that it gets caught almost every time. - Jack O'Connor

224

Generic answer

The standard "nop" in Python is the pass statement:

try:
    do_something()
except Exception:
    pass

Using except Exception instead of a bare except avoid catching exceptions like SystemExit, KeyboardInterrupt etc.

Python 2

Because of the last thrown exception being remembered in Python 2, some of the objects involved in the exception-throwing statement are being kept live indefinitely (actually, until the next exception). In case this is important for you and (typically) you don't need to remember the last thrown exception, you might want to do the following instead of pass:

try:
    do_something()
except Exception:
    sys.exc_clear()

This clears the last thrown exception.

Python 3

In Python 3, the variable that holds the exception instance gets deleted on exiting the except block. Even if the variable held a value previously, after entering and exiting the except block it becomes undefined again.

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• This is a better answer than the one that was accepted because it uses "except Exception:" instead of just "except:" which as others have pointed out will improperly swallow other things that you don't want to catch like SystemExit and KeyboardInterrupt. - aculich
• +1 It also clears the error which is important when running unittests and expecting exceptions - geographika
• Note that exc_clear was removed in python 3. docs.python.org/3/whatsnew/3.0.html#index-22. For some ways to address this in Python 3 see here: cosmicpercolator.com/2016/01/13/… - bcattle
• See stackoverflow.com/a/53575187/3140992 for quickly ignoring multiple exceptions - citynorman

133

There's a new way to do this coming in Python 3.4:

from contextlib import suppress

with suppress(Exception):
  # your code

Here's the commit that added it: http://hg.python.org/cpython/rev/406b47c64480

And here's the author, Raymond Hettinger, talking about this and all sorts of other Python hotness (relevant bit at 43:30): http://www.youtube.com/watch?v=OSGv2VnC0go

If you wanted to emulate the bare except keyword and also ignore things like KeyboardInterrupt—though you usually don't—you could use with suppress(BaseException).

Edit: Looks like ignored was renamed to suppress before the 3.4 release.

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• I'm not sure I like this solution... I guess the idea is we've replaced 3 lines with just 1 (the try, except, and pass are all merged into one.) The main thing I object to is how this introduces a new keyword that seems to vindicate something you probably shouldn't be doing... it seems like you should always at least log exceptions you're catching... - ArtOfWarfare
• This is equivalent to wrapping your code in a try...catch: pass, so if an exception is raised inside the block, execution will continue after the end of the block. - Jack O'Connor
• @JackO'Connor Well, that makes it rather useless... I thought it would just ignore exceptions as promised. - Navin
• @ArtOfWarfare What if I said, I'll give you an integer, but sometimes I'll give it to you in a singleton tuple, and I won't tell you when I do one or the other; now your job is to always give me back the integer? Perhaps you would appreciate being able to write something like with suppress(TypeError): return data[0] (longer example: pastebin.com/gcvAGqEP) - Air
• FYI, django revert the use of with suppress(Exception) on 2017-09 , because try/except performs better. Check this commits Reverted "Fixed #27818 -- Replaced try/except/pass with contextlib.su… - stackoverYC

13

Try this:

try:
    blah()
except:
    pass