[Python-Dev] unicode hell/mixing str and unicode as dictionary keys

[M.-A. Lemburg]

Delaney, Timothy (Tim) wrote:
> M.-A. Lemburg wrote:
> 
>> Perhaps we ought to add an exception to the dict lookup mechanism
>> and continue to silence UnicodeErrors ?!
> 
> I'd definitely consider a UnicodeError to be an indication that two
> objects are not equal. 

Not really: Python expects all strings to be ASCII whenever they
meet Unicode strings and have to be converted to Unicode. If a string
is not ASCII and thus causes the exception, there's not a lot you
can say, since you don't know the encoding of the string. All you
know is that it's not ASCII. Instead of guessing, Python then raises
an exception to let the programmer decide.

> At the very least, in the context of a dictionary
> lookup.

The point here is that a typical user won't expect any comparisons
to be made when dealing with dictionaries, simply because the fact
that you do need to make comparisons is an implementation detail.

So in this particular case silencing the exception might be the
more user friendly way of dealing with the problem.

That said, the problem still lingers in that dictionary, so it may
bite you in some other context, e.g. when iterating over the list
of keys.

-- 
Marc-Andre Lemburg
eGenix.com

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