[Python-Dev] Unicode as argument for 8-bit format strings

[M.-A. Lemburg]

Guido van Rossum wrote:
> 
> > No problem... :-) Its a simple fix: once %s in an 8-bit string
> > sees a Unicode object it will stop processing the string and
> > restart using the unicode formatting algorithm.
> 
> But the earlier items might already have incurred side effects
> (e.g. when rendering user code)...  Unless you save all the strings
> you got for reuse, which seems a pain as well.

Oh well... I don't think it's worth getting this 100% right. We'd
need quite a lot of code to store the intermediate results
and then have them reused during the Unicode %-formatting -- just
to catch the few cases where str(obj) does have side-effects:
the code would have to pass the partially rendered string
pasted together with the remaining format string to
the Unicode coercion mechanism and then fiddle the arguments right.

Which side-effects are you thinking about here ? Perhaps it
would be better to simply raise an exception in case '%s'
meets Unicode.

-- 
Marc-Andre Lemburg
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