[Python-Dev] Explicitly declaring expected exceptions for ablock

[Michael Chermside]

Dmitry Dvoinikov writes:
> The reason for that being self-tests with lots and lots of
> little code snippets like this:
>
> try:
>     c().foo()
> except TypeError:
>     pass

Paul Du Boise already responded explaining that PEP 343 probably handles
the task you want. I just wanted to mention that you may need to
reconsider the task. The above snippet is almost certainly incorrect.
I suspect that you wanted either:

   try:
       c().foo()
       fail('Should have raised TypeError')
   except TypeError:
       pass  # expected

or perhaps this:

    try:
        c().foo()
    except TypeError:
        fail('Should not have raised TypeError')

There ARE situations when you want to allow an exception (but not
necessarily expect it) and do nothing when it occurs, but I don't
find them all that common, and I certainly don't find them arising
in unit tests.

-- Michael Chermside