I think you are looking for the subs() method of symbolic expressions.
sage: var('A B')
(A, B)
sage: data = {A:1,B:2}
sage: expr = A+B
sage: expr
A + B
sage: expr.subs(data)
3
This will substitute as a dictionary. You can also do
sage: expr.subs(A=1,B=2)
3
if you like that syntax. Does that help?
@stanislav: As kcrisman does, note that it's more Pythonic to store key, value pairs in a dict than as a list of equations. That said, (a+b).subs_expr(*data) should work for lists of equations too.
Thanks, the second variant is the more comfortable for me, because then I can use a list of sets and put it into a for loop.
I think, the is no better way in sage because the way, you can use it in maxima can not be used in python. In maxima you can give the data list after an expression just by typing a comma like:
A+B,data
But I'm glad, the way with subs is working fine.
Asked: 2011-01-14 11:47:17 +0100
Seen: 540 times
Last updated: Jan 14 '11
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