numpy - create polynomial by its roots
For that purpose you will need to implement the multiplication of polynomial, that is, you need to make sure your product is able to generate the product of
(am * x^m + ... + a0) * (bn * x^n + ... + b0)
If your product is able to do this, then knowing the roots of
r1, ..., rk
You can write this as 
(x - r1) * ... * (x - rk)
and you need to repeatedly calculate the product here.
I'm trying to create a numpy.polynomial by the roots of the polynomial.
I could only find a way to do that by the polynomial's a's
The way it works now, for the polynomial x^2 - 3x + 2 I can create it like that:
poly1d([1, -3, 2])
I want to create it by its roots, which are -1, -2