(original) (raw)

Le Thu, 12 Sep 2013 08:05:44 -0700,

Ethan Furman <ethan@stoneleaf.us> a écrit :

> On 09/12/2013 07:43 AM, Antoine Pitrou wrote:
\> >
\> > Yeah, so this is totally silly. What you're basically saying is "we
\> > don't need TransformDict since people can re-implement it
\> > themselves".
\>
\> No, what I'm saying is that the "case-preserving" aspect of
\> transformdict is silly. The main point of transformdict is to
\> enable, for example, 'IBM', 'Ibm', and 'ibm' to all match up as the
\> same key. But why? Because you don't trust the user data. And if
\> you don't trust the user data you have to add the correct version of
\> the key yourself before you ever process that data, which means you
\> already have the correct version stored somewhere.

That's assuming there is an a priori "correct" version. But there might
not be any. Keeping the original key is important for different reasons
depending on the use case:

\- for case-insensitive dicts, you want to keep the original key for
presentation, logging and debugging purposes (\*)

\- for identity dicts, the original key is mandatory because the id()
value in itself is completely useless, it's just used for matching

(\*) For a well-known example of such behaviour, think about Windows
filesystems.