Imagine you have the following sympy expression:
'1.0 * H * L * * 3 * W * *2'
which contains the sp.Symbols variables=[H, L and W].
if this expression is lambdify-ed using sp.lambdify([sp.Symbol(vari) for vari in variables],'1.0 * H * L * * 3 * W * *2') you obtain a <function _lambdifygenerated(H, L, W)>.
However, I need to obtain a <function _lambdifygenerated(x)> where H=x[0], L=x[1], and W=x[2].
I have tried to xreplace{H: 'x[0]', W: 'x[1]', L: 'x[2]'} directly on the original expression '1.0 * H * L * * 3 * W * *2' and then lambdify with x as lambda.
This didn't work, but even if it would work after some tries I feel it is not the way to go.
Does anyone have any advice on how to deal with this?
Thank you very much!
You can preprocess the expression to replace all symbols with an IndexedBase, which you can think of as an array:
from sympy import *
L, H, W = symbols("L H W")
expr = 1.0 * H * L**3 * W**2
variables = [L, H, W]
x = IndexedBase("x")
# substitution dictionary
d = {v: x[i] for i, v in enumerate(variables)}
expr = expr.subs(d)
print(expr)
# out: 1.0*x[0]**3*x[1]*x[2]**2
f = lambdify(x, expr)
import inspect
print(inspect.getsource(f))
# out:
# def _lambdifygenerated(Dummy_22):
# return 1.0*Dummy_22[0]**3*Dummy_22[1]*Dummy_22[2]**2