Re Interest check in some delicious syntactic sugar for "except:pass"

Michael Rudolf spamfresser at ch3ka.de
Wed Mar 3 15:50:19 CET 2010


Am 03.03.2010 12:47, schrieb Oren Elrad:
> """ code involving somefile """
> try:
> ........os.remove(somefile)
> except:
> .......pass     # The bloody search indexer has got the file and I
> can't delete it. Nothing to be done.

You don't know that what you stated in your comment is true.
All you know is that there was an exception. To find the reason, you 
have to inspect the exception.
You escpecially do NOT know whether the file is removed or not.

OK, os.remove() might be a CPython builtin (not sure ATM), but in 
general all sort of crazy things can happen here, like ImportError 
raised by code in the lib or so.
And of course: a bare except: also catches ^C or SystemExit. That is 
almost certainly *not* what you want, right?

To your first question about a "silenced" keyword: you could emulate 
this with context managers I guess.

Something like (untested, just a quick mockup how it could look):



class silenced:
	def __init__(self, *silenced):
		self.exceptions=tuple(silenced) #just to be explicit
	def __enter__(self):
		return self			#dito1
	def __exit__(self, type, value, traceback):
		for ex in self.exceptions:
			if isinstance(value, ex):
				return True #supresses exception


So:

with silenced(os.Error):
	os.remove(somefile)

Would translate to:

try:
	os.remove(somefile)
except os.Error:
	pass

One nice thing about this approach would be that you can alias a set of 
exceptions with this:

idontcareabouttheseerrors=silenced(TypeError, ValueError, PEBCAKError, 
SyntaxError, EndOfWorldError, 1D10T_Error)

with idontcareabouttheseerrors:
	do_stuff()

Regards,
Michael



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