On Oct 1, 2009, at 5:54 PM, Nick Coghlan wrote:
I believe classes like fmt_braces/fmt_dollar/fmt_percent will be
part of
a solution, but they aren't a complete solution on their own. (Naming
the three major string formatting techniques by the key symbols
involved
is a really good idea though)
1. It's easy to inadvertently convert them back to normal strings.
If a
formatting API even calls "str" on the format string then we end up
with
a problem (and switching to containment instead of inheritance doesn't
really help, since all objects implement __str__).
Using containment instead of inheritance makes sure none of the
*other* operations people do on strings will appear to work, at least
(substring, contains, etc). I bet explicitly calling str() on a format
string is even more rare than attempting to do those things.
2. They don't help with APIs that expect a percent-formatted string
and
do more with it than just pass it to str.__mod__ (e.g. inspecting it
for
particular values such as '%(asctime)s')
True, but I don't think there's many such cases in the first place,
and such places can be fixed to not do that as they're found.
Until they are fixed, fmt_braces will loudly fail when used with that
API (assuming fmt_braces is not a subclass of str).
James
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