h[1] >>> from sympy.tensor import *
h[1] >>> M=Indexed('M')
h[1] >>> var('i j k', integer=1)
(i, j, k)
h[2] >>> eq=1+2*M(i,1)+3*j+4*M(i,2); eq
1 + 2*M(i, 1) + 3*j + 4*M(i, 2)
h[3] >>> for a in eq.as_Add():
... ie = []
... co = []
... for m in a.as_Mul():
... if isinstance(m, IndexedElement):
... ie.append(m)
... else:
... co.append(m)
... if ie:
... print Mul(*co), Mul(*ie)
...
4 M(i, 2)
2 M(i, 1)
h[3] >>>
If there's always only going to be one IndexedElement per term then
you could find them all with atoms and then find their coefficients
with coeff. But if you are worried about efficiency then you could
just check for an IndexedElement atom in a given term and find the
coeff of it when found:
h[3] >>> for a in eq.as_Add():
... ie = a.atoms(IndexedElement)
... if ie:
... assert len(ie) == 1
... ie = ie.pop()
... print a.coeff(ie), ie
...
4 M(i, 2)
2 M(i, 1)
If you need to know which argument it was then you can use the
enumerate to keep track of which "a" it was that had that term:
h[3] >>> for i, a in enumerate(eq.as_Add()):
... ie = a.atoms(IndexedElement)
... if ie:
... assert len(ie) == 1
... ie = ie.pop()
... print i, a.coeff(ie), ie
...
2 4 M(i, 2)
3 2 M(i, 1)
h[3] >>> print eq.args
(1, 3*j, 4*M(i, 2), 2*M(i, 1))
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