如何使用symPy和numPy将符号替换为矩阵

问题描述

我正在尝试用方程式中的两个符号代替每个符号的矩阵形式.

I'm trying to substitute two symbols in my equation for the matrix form of each of them.

我创建了一个换向器函数，形成了我的表达式:

I created a commutator function which formed my expression:

t, vS, = sy.symbols('t, vS', commutative = False)
hS = t + vS

eta = myComm(t,hS)

dHs = myComm(eta,hS)
print dHs.expand()

产生我想要的正确表达:

yielding the correct expression I want:

2*t*vS*t + t*vS**2 - t**2*vS - 2*vS*t*vS - vS*t**2 + vS**2*t

所以现在我希望用矩阵替换符号t和vS，但是当使用subs时出现错误，"unhashable type:'list'"，我认为这与矩阵的初始化或它们的初始化有关被适当替换，因为我对numPy和symPy都是新手.

So now I wish to substitute the symbols t and vS with matrices, however when using subs I get an error, "unhashable type: 'list'" I assume it has to do with my initialization of the matrices or how they should be properly substituted as I'm new to both numPy and symPy.

其余代码:

tRel = ([e0, 0],[0,e1])
vtmp = ([v0, v1],[v2,v3])

dHs = dHs.subs(t, tRel)
dHs = dHs.subs(vS, vtmp)
print dHs

推荐答案

也许使用 lambdify :

import sympy as sy
import numpy as np
from sympy.abc import x, y

z = ((x+y)**2).expand()
print(z)
# x**2 + 2*x*y + y**2
X = np.arange(6).reshape(2,3)
Y = np.arange(1,7).reshape(2,3)

f = sy.lambdify((x, y), z, 'numpy')
print(f(X, Y))
# [[  1   9  25]
#  [ 49  81 121]]

assert np.allclose(f(X, Y), (X**2 + 2*X*Y + Y**2))

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