How to check something is in a list with rich-comparison objects?

Wed Sep 16 03:23:28 EDT 2009

On 2009年9月16日 03:57:30 -0300, Gabriel Genellina wrote:
> En 2009年9月16日 03:36:32 -0300, Jason <jason.heeris at gmail.com>
> escribió:
>>> On Sep 16, 2:39 am, "Gabriel Genellina" <gagsl-... at yahoo.com.ar> wrote:
>>> Looks like a bug in pysvn. Some class (whatever
>>> pysvn.wc_notify_action.status_completed is) is not well written. When
>>> compared against something unknown, it should return NotImplemented
>>> instead of raising AttributeError.
>> (top posting corrected)
>>> I will raise this with pysvn, if I can ever find their issue reporting
>> system.
>>>> In the meantime, I suppose I can only do this by traversing the list
>> with a loop and catching exceptions. Ugly, but seems to be the only
>> way.
>> You might use a list subclass and override its __contains__ method (and
> perhaps index() too). It's the same ugly code, but at least expressions
> like:
>> 'foo' in some_list
>> would still work.

Or you can wrap each item in an object that does the right thing.
# untested
class Wrapper:
 # Thin wrapper to make equals comparisons work correctly
 def __init__(self, payload):
 self.payload = payload
 def __eq__(self, other):
 payload = self.payload
 try:
 return payload.__eq__(other)
 except AttributeError:
 return other.__eq__(payload)
some_list = map(Wrapper, some_list)
-- 
Steven