[Python-Dev] Why not support user defined operator overloading ? (original) (raw)

Ned Batchelder ned at nedbatchelder.com
Sun Sep 29 21:35:27 CEST 2013

On 9/29/13 11:06 AM, Xavier Morel wrote:

This is more of a python-ideas subject.

And one of the reasons likely is that it would require significantly reworking the grammar to handle a kind of user-defined opname (similar to name, but for operator tokens), with user-defined priority and associativity, and the ability to import operators (or define how and when operators become available compared to their definition) That's a huge amount of complexity with little to gain.

It isn't just a matter of a more complex parser: where would the parser get the information about these new operators? The obvious first answer is that they would be defined as part of classes, but that means the operator definition is in an imported module some place. The importing module couldn't even be parsed until the class was imported. This is a completely different compilation and execution model than Python has now.

Now you can compile a Python module without any access to the modules it will eventually import. Importing is a run-time operation. If you want user-defined classes to be able to define new syntax, then importing has to happen at compile time. That's a completely different language.

--Ned.

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