Comment #3 on issue 1838 by asmeurer: Add support for [0]*S(5), etc.
http://code.google.com/p/sympy/issues/detail?id=1838
The motivation was this conversation on IRC:
xvedejas joined the chat room.
[11:43am] xvedejas: can anyone here help me with sympy?
[11:43am] xvedejas: it seems to have interfered with my python types
causing weird things to happen
[11:44am] xvedejas: TypeError: can't multiply sequence by non-int of
type 'Integer'
[11:56am] asmeurer: hi xvedejas
[11:56am] asmeurer: can you give me some code that causes that?
[12:10pm] xvedejas: self.n = 5
[12:10pm] xvedejas: List = [0] * self.n
[12:11pm] xvedejas: just like that basically
[12:11pm] xvedejas: I actually fixed the problem by only importing sympy
within a smaller scope, but it's
strange that it would cause that anyways
[12:11pm] asmeurer: would that normally work?
[12:11pm] xvedejas: yes
[12:11pm] xvedejas: [0] * 5 == [0, 0, 0, 0, 0]
[12:11pm] asmeurer: I did not know about that feature.
[12:12pm] asmeurer: what is self here?
[12:12pm] asmeurer: probably the easiest fix would be [0]*int(self.n)
[12:12pm] xvedejas: yes but I'd have to do that to every integer it seems
[12:13pm] xvedejas: I've fixed it however by only importing sympy in the
method that uses it
[12:13pm] asmeurer: what ever you are doing is sympifying self.n, so if you
avoid that somehow, it should to it
too I guess
[12:14pm] asmeurer: are you doing exactly self.n = 5 or self.n = result of
some calculation?
[12:14pm] xvedejas: it's the result of a calculuation... that has nothing
to do with sympy
[12:14pm] asmeurer: well it is somehow being converted to a sympy Integer
[12:14pm] xvedejas: alright
[12:14pm] asmeurer: which will happen if it is the result of any sympy
calculation
[12:15pm] xvedejas: at any rate, I'd like to say thanks to the creaters of
sympy, I'm using it for a math program
I'll be presenting at a couple conferences
[12:15pm] asmeurer: but if list.__mul__ doesn't call __int__, I don't think
there is a way that we can fix that
[12:15pm] asmeurer: unless Int.__rmul__ would work
[12:15pm] asmeurer: hmm...
[12:16pm] asmeurer: I'm going to grab lunch now, but I might play around
with that after words
[12:16pm] xvedejas: alright
[12:16pm] asmeurer: glad you are finding sympy useful!
[12:16pm] xvedejas: simplified some matrix algebra greatly :)
[12:17pm] asmeurer: by the way, if your presentation is posted online, we
would like to know about it so we can
add it to http://docs.sympy.org/outreach.html
[12:17pm] You have set yourself away with "lunch".
[12:17pm] xvedejas: cool
[1:05pm] You have returned from away.
[1:12pm] asmeurer: xvedejas: I think I could implement it so that
sympify(5)*[0] would work, but it seems that
list.__mul__(Integer) doesn't return NotImplemented, so __rmul__ (i.e.,
[0]*sympify(5)) won't work
[1:23pm] howlymowly left the chat room. (Remote host closed the connection)
[1:29pm] howlymowly joined the chat room.
[1:29pm] howlymowly left the chat room. (Remote host closed the connection)
[1:36pm] asmeurer: actually, the overridding works in Python 2.5
[1:50pm] asmeurer: OK, nevermind, it can work anywhere
[1:50pm] asmeurer: http://github.com/asmeurer/sympy/tree/list-int-mul.
[2:10pm] asmeurer: xvedejas:
http://code.google.com/p/sympy/issues/detail?id=1838
[2:11pm] asmeurer: Thanks for the report. It's always fun to learn about
new Python syntactical features.
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