How do I fill a symbolic N-dim zero array in python?-CodePudding

I've initialized the following array:

ChristSymb=sym.Array(np.zeros((d,d,d),dtype=int))

and I've been trying to fill it up with symbolic expressions using a for loop, but after compiling appear the following error

TypeError: immutable N-dim array

What's wrong with the array definition that cannot be modified? How can I solve it?

CodePudding user response：

This is because sym.Array is actually an abbreviation for ImmutableDenseNDimArray. This information is available in the docs. What you need to do is use the mutable version class called MutableDenseNDimArray like this:

import sympy as sym
import numpy as np

ChristSymb = sym.MutableDenseNDimArray(np.zeros((d, d, d), dtype=int))

CodePudding user response：

Array is an abbrevation for ImmutableDenseNDimArray. Immutable means that its component elements cannot be changed once the array is defined.

You can create a mutable array of zeros with one of these ways:

In [2]: MutableDenseNDimArray.zeros(3,3,3)
Out[2]: [[[0, 0, 0], [0, 0, 0], [0, 0, 0]], [[0, 0, 0], [0, 0, 0], [0, 0, 0]], [[0, 0, 0], [0, 0, 0], [0, 0, 0]]]

This creates a mutable array of zeros (note that you don't need NumPy, as SymPy also has the zeros(...) function).

Otherwise, convert the immutable array to a mutable array:

In [3]: Array.zeros(3,3,3).as_mutable()
Out[3]: [[[0, 0, 0], [0, 0, 0], [0, 0, 0]], [[0, 0, 0], [0, 0, 0], [0, 0, 0]], [[0, 0, 0], [0, 0, 0], [0, 0, 0]]]