Discussion about PEP 234: iterators

[Nathaniel Gray]

Tim Hochberg wrote:
> [snip discussion of consistency of "if thing in dict:"]
>
> Unfortunately, people tend to think of a dictionary as containing keys
> more than they think of it as containing definitions (values). So the form
> you propose is better from that point of view. It's also probably more
> useful in a practical sense as well. It is kind of distressing that it's
> not consistent with the correspondence that's set up between
> keys<->indices and values<->values though.

Hmm... I tend to think of a dictionary as containing values more than keys. 
 The keys are just there so you can get to the values, right?  Others tend 
to think dicts contain (key, value) pairs.  Everybody has a different 
opinion on this one.  Rather than supplying an arbitrary default, which 
would lead to confusion, how about we let the programmer specify things 
explicitly.

How about we make it:
if key in dict.keys():
and
if value in dict.values():
and maybe even
if (key, value) in dict.items():

That way it's perfectly clear what the programmer intended.  I think 
there's a really good chance of Guido accepting this proposal, and I've 
already written a fully backwards-compatible patch.  Anybody up for a trip 
back in time?

-n8

-- 
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             Nathaniel Gray
   California Institute of Technology
     Computation and Neural Systems
     n8gray <at> caltech <dot> edu
_.~'^`~._.~'^`~._.~'^`~._.~'^`~._.~'^`~._