Overriding special methods

[AaronKelly]

Hello all,
I was wondering if anyone has had any luck implementing the special method __pow__? I tried searching for others implementation and tried adding c extension code for the objxxx.c files but when trying to override the object in the class initiator I get the following:

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> import CustomList
> a = CustomList(1,2,3)
> a**2
>Traceback (most recent call last):
	File "<stdin>", line 1, in <module>
	TypeError: unsupported types for <listcomp>: 'CustomList', 'int'

[pythoncoder]

It looks as if the special method hasn't been implemented. This works, returning 8:

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class Foo():
    def __init__(self, v):
        self.v = v
    def __mul__(self, val):
        return self.v * val

f = Foo(4)
f * 2

but this doesn't:

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class Bar():
    def __init__(self, v):
        self.v = v
    def __pow__(self, val):
        return self.v ** val

f = Bar(4)
f ** 2

throwing

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Traceback (most recent call last):
  File "<stdin>", line 8, in <module>
TypeError: unsupported types for : 'Bar', 'int'
>>> 

You might want to raise it on GitHub.

[AaronKelly]

Thanks for the feedback @pythoncoder

I found the piece of code that allows for power overloading in objtype.c and replacing

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    [MP_BINARY_OP_POWER]
    [MP_BINARY_OP_INPLACE_POWER]

for

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    [MP_BINARY_OP_POWER] = MP_QSTR___pow__,
    [MP_BINARY_OP_INPLACE_POWER] = MP_QSTR___iadd__,

however the only issue now is that when I try with objects that shouldn't have a power I get

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TypeError: unsupported types for __pow__: 'tuple', 'int'

Instead of say

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TypeError: unsupported types for **: 'tuple', 'int'

[pythoncoder]

I see you've raised this on GitHub so doubtless the maintainers will comment.

In your original post you refer to a CustomList class. I don't know if you're subclassing a list here, but if so be aware that MicroPython support for subclassing built-in types is limited. https://github.com/micropython/micropyt ... ifferences Obviously it's irrelevant to the ** problem but I thought it worth a mention.

[AaronKelly]

The overloading of builtin types was just an example to show the error in the error message as it refers to the binary operation as __pow__ instead of **.