On 16/07/2015 08:09, Mark Lawrence wrote:
On 16/07/2015 07:37, Ben Finney wrote:
Ethan Furman <et...@stoneleaf.us> writes:
On 07/15/2015 10:53 PM, Ben Finney wrote:
Are those the ‘__contains__’, ‘__getitem__’ methods? What actually
is the API of a mapping type, that would need to be customised for
this application?
The problem is that potential key matches are found by hashes
For the Python ‘dict’ type, yes. I already know that I don't want that
type, I want a custom mapping type which matches keys according to the
algorithm I specify.
So, I'm not asking “how do I make ‘dict’ do this?”. I am instead asking
“how do I implement a custom type which can duck-type for ‘dict’ but
have a different key-lookup implementation?”.
https://docs.python.org/3/reference/datamodel.html?emulating-container-types
<quote>
The collections module provides a MutableMapping abstract base class to
help create those methods from a base set of __getitem__(),
__setitem__(), __delitem__(), and keys()
</quote>
Hence
https://docs.python.org/3/library/collections.abc.html#collections.abc.MutableMapping
Hunting for examples got me to
http://code.activestate.com/recipes/578096-a-mutablemapping-that-can-use-unhashable-objects-a/
so fingers crossed, I'm just hoping that we're going in the right
direction.
Drat, should have scrolled down one more page on the activestate recipe,
Stephen D'Aprano comment.
<quote>
This is very ingenious, but I wouldn't want to touch it with a ten foot
pole for production code
</quote>
Eric Snow replied.
<quote>
Oh yeah. I wouldn't use it in production either. :) I expect you could
iron out the wrinkles, but there are better solutions.
</quote>
--
My fellow Pythonistas, ask not what our language can do for you, ask
what you can do for our language.
Mark Lawrence
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