[Python-Dev] On suppress()'s trail blazing (was Re: cpython: Rename contextlib.ignored() to contextlib.ignore()) (original) (raw)

Terry Reedy tjreedy at udel.edu
Fri Oct 18 04:33:53 CEST 2013

On 10/17/2013 7:35 PM, Nick Coghlan wrote:

On 18 Oct 2013 06:59, "Xavier Morel" <catch-all at masklinn.net_ _<mailto:catch-all at masklinn.net>> wrote: > > On 2013-10-17, at 22:11 , Ethan Furman wrote: > > > On 10/17/2013 01:03 PM, Terry Reedy wrote: > >> > >> class suppress: > >> def init(self, *exceptions): > >> self.exceptions = exceptions > >> def exit(self, etype, eval, etrace): > >> return etype in self.exceptions > > > > This fails when etype is a subclass of the exceptions, as mentioned in the original issue.

There are two other failures; see below. I know better than to post code without testing or saying 'untested'; I just wish I would always remember...

> That's fixed by using issubclass and does not infirm Terry's point does it?

Yeah, it looks like it's worth switching to the class based implementation in this case. I guess I'm too accustomed to that being the more complex alternative, as I hadn't even tried it :)

With two more changes (add enter, account for etype is None), the suppress tests pass.

import unittest

class suppress: def init(self, *exceptions): self.exceptions = exceptions def enter(self): pass def exit(self, etype, val, tb): return etype is None or issubclass(etype, self.exceptions)

class Testsuppress(unittest.TestCase):

 def test_no_exception(self):
     with suppress(ValueError):
         self.assertEqual(pow(2, 5), 32)

 def test_exact_exception(self):
     with suppress(TypeError):
         len(5)

 def test_multiple_exception_args(self):
     with suppress(ZeroDivisionError, TypeError):
         len(5)

 def test_exception_hierarchy(self):
     with suppress(LookupError):
         'Hello'[50]

unittest.main()

Ran 4 tests...OK

-- Terry Jan Reedy

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