Python-如何将矩阵与符号和 0 相乘 [英] Python-How to multiply matrix with symbols and 0s

问题描述

我是 python 的新手，但是有没有办法将矩阵与 0 和符号相乘?例如，见下文:

I am brand new to python, but is there any way to multiply matrices with both 0's and symbols? For example, see below:

import sympy as sym
import numpy as np
teams=np.matrix([[1,2],[3,4]])
teams=teams-1
n=4
x,a,b=sym.symbols('x a b')
X=np.empty((n,n), dtype=object)
Y=np.empty((n,n), dtype=object)
Z=np.empty((n,n), dtype=object)
for i in range(n):
    for j in range(n):
            if j==i:
                X[i,j]=x
            elif ([i,j] in teams.tolist()):
                Y[i,j]=a
            elif ([j,i] in teams.tolist()):
                Y[i,j]=a
            else:
                Z[i,j]=b
for i in range(n):
    for j in range(n):
        if X[i,j]==None:
            X[i,j]=0
        if Y[i,j]==None:
            Y[i,j]=0
        if Z[i,j]==None:
            Z[i,j]=0

print(np.matmul(X,Y))

TypeError                                 Traceback (most recent call last)
<ipython-input-189-00b753462a2d> in <module>
      2 print(Y)
      3 print(Z)
----> 4 print(np.matmul(X,Y))

TypeError: ufunc 'matmul' not supported for the input types, and the inputs could not be safely coerced to any supported types according to the casting rule ''safe''

我知道它为什么会搞砸，我正在尝试将一个符号乘以一个数字，但我想知道是否有任何方法可以让这个认识到符号乘以 0 只是零，如果被添加到，应该被忽略另一个符号.

I know why it is messing up, I am trying to multiply a symbol by a number, but I was wondering if there was anyway to make this recognize that a symbol times 0 is just zero and should be disregarded if being added to another symbol.

推荐答案

我用 print(np.dot(X,Y)) 而不是 print(np.matmul) 测试了你的代码(X,Y)) 并且它起作用了.根据文档 np.matmul 优于 np.dot 矩阵乘法，但我无法弄清楚如何使用 np 来做.矩阵.我尝试了 np.matmul(X, Y, cast='unsafe')，但结果是同样的错误.我不认为错误是由加 0 或乘以 0 引起的，sympy 能够进行简化.

I tested your code with print(np.dot(X,Y)) instead of print(np.matmul(X,Y)) and it worked. According to the documentation np.matmul is preferred over np.dot for matrix multiplication, but I wasn't able to figure out how to do it using np.matmul. I tried np.matmul(X, Y, casting='unsafe'), but the same error resulted. I don't think the error is caused by adding 0 or multiplying by 0, sympy is able to do simplifications.

例如

x = sym.symbols('x')
print(x + 0)
print(x*0)
print(3*x + 5*x)

按预期返回 x、0 和 x*8.

returns just as expected x, 0 and x*8.

希望这对您有所帮助.

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