[issue25412] __floordiv__ in module fraction fails with TypeError instead of returning NotImplemented

2019-01-11 Thread Sergey Shashkov 


Sergey Shashkov  added the comment:

This patch actually fixes the problem:

https://bugs.python.org/issue35588
https://github.com/python/cpython/commit/3a374e0c5abe805667b71ffaaa7614781101ff4c




from fractions import Fraction
import operator

class Goo:
__radd__, __rdivmod__, __rfloordiv__, __rmod__, __rmul__, __rpow__, 
__rsub__, __rtruediv__ = [lambda a, b: 'ok'] * 8

for func in operator.add, operator.sub, operator.mul, operator.truediv, 
operator.pow, operator.mod, operator.floordiv, divmod:
print(func.__name__, func(Fraction(1), Goo()))

--
nosy:  -mark.dickinson, oscarbenjamin, vstinner
pull_requests: +11085
resolution:  -> fixed
stage:  -> patch review
status: open -> closed

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[issue25412] __floordiv__ in module fraction fails with TypeError instead of returning NotImplemented

2015-10-15 Thread Sergey Shashkov 

New submission from Sergey Shashkov:

__floordiv__ in module fraction fails with TypeError instead of returning 
NotImplemented when modulo is a class without __rtruediv__ or __mul__.

Code sample:

class Foo(object):
def __rdivmod__(self, other):
return 'rdivmod works'

from fractions import Fraction
a = Fraction(1,1)
b = Foo()
print(divmod(1, b))
print(divmod(a, b))



__divmod__ in Fraction is inherited from class Real (numbers.py):
def __divmod__(self, other):
return (self // other, self % other)

So __floordiv__ and __mod__ are called. 

def __floordiv__(a, b):
"""a // b"""
return math.floor(a / b)

def __mod__(a, b):
"""a % b"""
div = a // b
return a - b * div

__floordiv__ if fractions.py makes a true division, and __mod__ makes 
multiplication.



The following code will fix the problem:


def __divmod__(self, other):
if isinstance(a, numbers.Complex):
return (self // other, self % other)
else:
return NotImplemented

--
components: Library (Lib)
messages: 253046
nosy: ShashkovS
priority: normal
severity: normal
status: open
title: __floordiv__ in module fraction fails with TypeError instead of 
returning NotImplemented
type: behavior
versions: Python 2.7, Python 3.2, Python 3.3, Python 3.4, Python 3.5, Python 3.6

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[issue25412] __floordiv__ in module fraction fails with TypeError instead of returning NotImplemented

2015-10-15 Thread Sergey Shashkov 

Sergey Shashkov added the comment:

def __floordiv__(a, b):
"""a // b"""
if isinstance(b, numbers.Complex):
return math.floor(a / b)
else:
return NotImplemented

And the same for __mod__.

--

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[issue25412] __floordiv__ in module fraction fails with TypeError instead of returning NotImplemented

2015-10-16 Thread Sergey Shashkov 

Sergey Shashkov added the comment:

OK,

then we should not change numbers.py.

And in fractions.py:

def __floordiv__(a, b):
"""a // b"""
if isinstance(b, numbers.Complex) or hasattr(b, '__rtruediv__'):
fr = a / b
if fr != NotImplemented:
return math.floor(a / b)
else:
return NotImplemented
else:
return NotImplemented

--

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[issue25412] __floordiv__ in module fraction fails with TypeError instead of returning NotImplemented

2015-10-16 Thread Sergey Shashkov 

Sergey Shashkov added the comment:

Bad idea, just


def __floordiv__(a, b):
"""a // b"""
if isinstance(b, numbers.Complex):
return math.floor(a / b)
else:
return NotImplemented

If b is inherited from number, real, complex, Fraction and etc, then a of type 
Fraction knows, how do make a division.
Otherwise may be b has __rfloordiv__, that khows how to be divided by Fraction.

--

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[issue25412] __floordiv__ in module fraction fails with TypeError instead of returning NotImplemented

2015-10-16 Thread Sergey Shashkov 

Sergey Shashkov added the comment:

...
def forward(a, b):
if isinstance(b, (int, Fraction)):
return monomorphic_operator(a, b)
elif isinstance(b, float):
return fallback_operator(float(a), b)
elif isinstance(b, complex):
return fallback_operator(complex(a), b)
else:
return NotImplemented
forward.__name__ = '__' + fallback_operator.__name__ + '__'
forward.__doc__ = monomorphic_operator.__doc__

def reverse(b, a):
if isinstance(a, numbers.Rational):
# Includes ints.
return monomorphic_operator(a, b)
elif isinstance(a, numbers.Real):
return fallback_operator(float(a), float(b))
elif isinstance(a, numbers.Complex):
return fallback_operator(complex(a), complex(b))
else:
return NotImplemented
...
so division is possible only with int, Fraction, float, complex, 
numbers.Rational, numbers.Real, numbers.Complex.
For all of them "isinstance(b, numbers.Complex)" is true

--

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[issue25412] __floordiv__ in module fraction fails with TypeError instead of returning NotImplemented

2015-10-16 Thread Sergey Shashkov 

Changes by Sergey Shashkov :


--
hgrepos: +320

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[issue25412] __floordiv__ in module fraction fails with TypeError instead of returning NotImplemented

2015-10-16 Thread Sergey Shashkov 

Changes by Sergey Shashkov :


--
hgrepos:  -320

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[issue25412] __floordiv__ in module fraction fails with TypeError instead of returning NotImplemented

2015-10-16 Thread Sergey Shashkov 

Changes by Sergey Shashkov :


--
hgrepos: +321
keywords: +patch
Added file: http://bugs.python.org/file40797/fractions_truediv_fix.patch

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