On 02/20/2012 04:35 PM, Chris Smith wrote:
On Tue, Feb 21, 2012 at 3:02 AM, Alan Bromborsky <[email protected]
<mailto:[email protected]>> wrote:
Is there a simple way of extracting the following from a sympy
expression -
expr = expr_0 + expr_1+...+expr_n
where in each expr_j (j>0) there is a factor a_j which is a symbol
(in my case noncommuting). I need to extract the
parts of expr_j that multiplies a_j for all the expr_1. Only one
a_j is a factor in expr_j . That is if one can rewrite
expr = expr_0 + expr'_1*a_1+...+expr'_n*a_n
and then extract (expr_0,expr'_1,...,expr'_n)
Is this different than you were writing about in the "not reinventing"
message? I had written
>>> eq=a*A+b*c*B+d
>>> zip(*[arg.args_cnc() for arg in eq.args])
[([a], [d], [b, c]), ([A], [], [B])]
The first list of lists is a list of the factors that are in front of
the noncommutative parts of your terms. If you want them as
expressions, remultiply them:
>>> eq=a*A+b*c*B+d
>>> co, nc = zip(*[arg.args_cnc() for arg in eq.args])
>>> [Mul(*c) for c in co]
[a, d, b*c]
>>> nc
([A], [], [B])
Can you give a concrete example of input and output that you would like?
/c
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My problem is that I am a lousy speller and I spelled the commutative
keyword in symbol wrong!!!!
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