[Python-Dev] PEP 8: mention bare 'except:' (original) (raw)

A.M. Kuchling amk at amk.ca
Fri Dec 22 14:05:47 CET 2006

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http://www.python.org/sf/411881 is a bug about removing use of 'except:' in stdlib code. In many cases the intent is to catch one particular exception such as ImportError or AttributeError, but catching all exceptions can disguise other problems.

Should PEP 8 mention this issue? Here's some proposed text for discussion:

• When catching exceptions, mention specific exceptions whenever possible instead of using a bare 'except:' clause.

  For example, use::

  try:
      import platform_specific_module
  except ImportError:
      platform_specific_module = None 

  A bare 'except:' clause will catch SystemExit and KeyboardInterrupt exceptions, making it harder to interrupt a program with Control-C, and can disguise other problems. If you want to catch all exceptions that signal program errors, use 'except StandardError:'.

  A good rule of thumb is that you should only use 'except:' if the exception handler will be printing out or logging the traceback; at least the user will be aware that an error has occurred.

--amk

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