On 14/09/2013 01:49, Steven D'Aprano wrote:
On Fri, Sep 13, 2013 at 11:45:16PM +0200, Antoine Pitrou wrote:
Ok, I have a better (IMO) proposal:
>>> d = TransformDict(str.casefold, {'Foo': 1})
>>> d.getitem('foo')
('Foo', 1)
>>> d.getitem('bar')
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
KeyError: 'bar'
Is it more common to want both the canonical key and value at the same
time, or to just want the canonical key? My gut feeling is that I'm
likely to have code like this:
d = TransformDict(...)
for key in data:
key = d.get_canonical(key)
value = d[key]
print("{}: {}".format(key, value))
I think must be missing something. I thought that iterating over the
dict would yield the original keys, so if you wanted the original key
and value you would write:
for key, value in data.items():
print("{}: {}".format(key, value))
and if you wanted the transformed key you would apply the transform
function to the key.
in which case having a single call to return both will be great:
for key in data:
key, value = d.getitem(key)
print("{}: {}".format(key, value))
but I'm really not sure. Maybe Ethan is right.
I think these sorts of associated questions are why some people
(Raymond, Nick) want to see the proposal live outside of the standard
library for a while first. The general idea is great, but we're going to
bike shed the API without having much idea of how it will actually be
used.
So, my suggestion is this:
- Let's add __transform__ to dicts for 3.4, similar to __missing__, and
see how people end up using it in the real world.
- Then, in 3.5, we can make a much better informed decision about the
best API for a TransformedDict front-end to __transform__.
+1 on __transform__ method on dicts.
+0 on TransformedDict in 3.4
+1 on waiting for 3.5 based on experience on using __transform__.
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