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Are the right side magic methods supposed to work? #2056

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malinoff opened this Issue Dec 28, 2017 · 1 comment

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@malinoff

malinoff commented Dec 28, 2017

I'm not sure if this is a bug report or a feature request, but as of cython 0.27.3 __radd__, __rtruediv__ and other right side magic methods do not work:

In [1]: %load_ext Cython

In [2]: %%cython
   ...: cdef class Example:
   ...:   def __radd__(self, other):
   ...:     print('radd', self, other)
   ...:   def __rtruediv__(self, other):
   ...:     print('rtruediv', self, other)
   ...:

In [3]: 3 + Example()
---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
<ipython-input-3-b54d8dd2451f> in <module>()
----> 1 3 + Example()

TypeError: unsupported operand type(s) for +: 'int' and '_cython_magic_c1fde2d95cc29b87ed98f696ccfef975.Example'

In [4]: 'foo' / Example()
---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
<ipython-input-4-1e29a35d9b28> in <module>()
----> 1 'foo' / Example()

TypeError: unsupported operand type(s) for /: 'str' and '_cython_magic_c1fde2d95cc29b87ed98f696ccfef975.Example'

In [5]: import Cython

In [6]: Cython.__version__
Out[6]: '0.27.3'

I'm using the following workaround, but it looks ugly:

In [7]: %%cython
   ...: cdef class Example:
   ...:   def __add__(other, self):
   ...:     print('add', self, other)
   ...:   def __truediv__(other, self):
   ...:     print('truediv', self, other)
   ...:

In [8]: 3 + Example()
add <_cython_magic_45c6eacd188f8181199b3c76f32cba5d.Example object at 0x109d7a0f0> 3

In [9]: 'foo' / Example()
truediv <_cython_magic_45c6eacd188f8181199b3c76f32cba5d.Example object at 0x109d7a110> foo

and doesn't really work if we switch operands:

In [10]: Example() + 3
add 3 <_cython_magic_45c6eacd188f8181199b3c76f32cba5d.Example object at 0x109d7a110>

In [11]: Example() / 'foo'
truediv foo <_cython_magic_45c6eacd188f8181199b3c76f32cba5d.Example object at 0x109468e60>

I'm not familiar with cython codebase, but a quick search through the source, issues and PRs doesn't show anything related.

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robertwb Dec 30, 2017

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robertwb commented Dec 30, 2017

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