sympy : expression simplification

Question

I begin with sympy python lib.

If, I have this expression

from sympy.abc import a,b,c,p,q
e = p * ( a + b ) + q * ( a + c )

how I can use a,b,c as factor ? like

a(p+q) + b*p + c*q

Answer 1

collect is indeed the function you want. You can pass multiple symbols as the collection variable to collect them all. And as you noticed, collect will not expand your expression first, so if you want that, you have to do it yourself with expand.

In [15]: collect(e.expand(), [a, b, c])
Out[15]: a⋅(p + q) + b⋅p + c⋅q

Answer 2

from sympy.abc import a,b,c,p,q
from sympy import collect, expand
e = p * ( a + b ) + q * ( a + c )

print e
print expand(e)
print collect(expand(e),a)