New submission from Aaron Meurer <asmeu...@gmail.com>:
This works in Python 2.5 but not in Python 2.6.
If you do [0]*5, it gives you [0, 0, 0, 0, 0]. I tried getting this to work
with SymPy's Integer class, so that [0]*Integer(5) would return the same, but
unfortunately, the sequence multiplication doesn't seem to return
NotImplemented properly allowing it to be overridden in __rmul__. Overridding
in regular __mul__ of course works fine. From sympy/core/basic.py (modified):
# This works fine
@_sympifyit('other', NotImplemented)
def __mul__(self, other):
if type(other) in (tuple, list) and self.is_Integer:
return int(self)*other
return Mul(self, other)
# This has no affect.
@_sympifyit('other', NotImplemented)
def __rmul__(self, other):
if type(other) in (tuple, list, str) and self.is_Integer:
return other*int(self)
return Mul(other, self)
In other words, with the above, Integer(5)*[0] works, but [0]*Integer(5) raises
TypeError: can't multiply sequence by non-int of type 'Integer' just as it does
without any changes. See also my branch at github with these changes
http://github.com/asmeurer/sympy/tree/list-int-mul.
Another option might be to just have the list.__mul__(self, other) try calling
int(other).
SymPy has not yet been ported to Python 3, so I am sorry that I cannot test if
it works there.
----------
messages: 99629
nosy: Aaron.Meurer
severity: normal
status: open
title: Have sequence multiplication call int() or return NotImplemented so that
it can be overridden with __rmul__
type: behavior
versions: Python 2.6
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Python tracker <rep...@bugs.python.org>
<http://bugs.python.org/issue7972>
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