Sage Integers are incompatible with Python fraction.Fraction, statistics.mean, itertools.permutations #28234
Description
fraction.Fraction
In Sage 8.8 the code:
sage: from fractions import Fraction
sage: Fraction(1, 1)
raises the following error:
---------------------------------------------------------------------------
TypeError Traceback (most recent call last)
<ipython-input-4-0c4690dff1ca> in <module>()
----> 1 Fraction(Integer(1), Integer(1))
/Applications/SageMath-8.8.app/Contents/Resources/sage/local/lib/python2.7/fractions.pyc in __new__(cls, numerator, denominator)
152 isinstance(denominator, Rational)):
153 numerator, denominator = (
--> 154 numerator.numerator * denominator.denominator,
155 denominator.numerator * numerator.denominator
156 )
TypeError: unsupported operand type(s) for *: 'builtin_function_or_method' and 'builtin_function_or_method'
This appears to be because of the fact that Python ints have numerator and denominator properties whereas for Sage integers these are methods. Therefore Fraction does not call these attributes leading to the crash
Note, turning off the pre-parser or doing:
sage: Fraction(int(1), int(1))
Fraction(1, 1)
works.
One solution to this would be to decorate sage.rings.integer.Integer.numerator() and sage.rings.integer.Integer.denominator() with the @property decorator, but this will likely cause a large number of systems to break.
Earlier report of this issue
in #10928, comment 14 (a ticket about getitem of numpy matrix using Sage integers).
statistics.mean (see #29662)
Although the as_integer_ratio mechanism has been added to Python, statistics._exact_ratio does not use as_integer_ratio because it sees the Sage numbers' numerator and denominator methods and tries to use them as properties.
itertools.permutations
┌────────────────────────────────────────────────────────────────────┐
│ SageMath version 9.5.beta7, Release Date: 2021-11-18 │
│ Using Python 3.9.9. Type "help()" for help. │
└────────────────────────────────────────────────────────────────────┘
sage: import itertools
sage: list(itertools.permutations(range(3),int(2)))
[(0, 1), (0, 2), (1, 0), (1, 2), (2, 0), (2, 1)]
sage: list(itertools.permutations(range(3),2))
---------------------------------------------------------------------------
TypeError Traceback (most recent call last)
<ipython-input-8-a9f97c1deeca> in <module>
----> 1 list(itertools.permutations(range(Integer(3)),Integer(2)))
TypeError: Expected int as r
see https://bugs.python.org/issue30537#msg295000
CC: @jdemeyer @sagetrac-mcbell @slel @videlec @simon-king-jena @posita @tscrim
Component: basic arithmetic
Keywords: days100
Author: Mark Bell
Branch/Commit: public/28234 @ 4977867
Issue created by migration from https://trac.sagemath.org/ticket/28234