On 8/12/2012 7:55 AM, Giacomo Alzetta wrote:
What I mean is: when you implement a new type as a C extension you have to provide special methods through the NumberMethods struct. In this struct both the power and in-place power operations have three arguments.
I am not really sure why the latter is true. Probably 'consistency' at the special method level, with __pow__. As Steven points out, it is not needed to implement normal Python code.
This is one area of Python where the design is a bit messy. I believe the very existence of __ipow__ is a matter of consistency than of known use cases. Guido was not sure which __ixxx__ would ever be needed (for mutable objects), so he just put them all in.
At the Python level, both __pow__ and __ipow__ are also documented in the manual as having an optional, third, modulo parameter. __rpow__ is defined as binary, but that is a mistake
>>> int.__rpow__(3, 5, 4) 1
Now, suppose I implement the three argument variant of the in-place power in a class.
Are you actually planning to do this, or is this purely theoretical?
No user would be able to call my C function with a non-None third argument,
Not true. Whether the function is coded in Python or C cls.__ipow__(base, exp, mod) # or base.__ipow__(exp, mod)
while he would be able to call the normal version with the third argument.
That can also be done directly >>> int.__pow__(5, 3, 4) 1 -- Terry Jan Reedy -- http://mail.python.org/mailman/listinfo/python-list
