Error with arrays in Python

The problem is that you are not passing a matrix but a string of text, if you want to enter the matrix the way you do you need to parse the input string and pass it to a list of lists or a bidimensional array of Numpy.

• Entry of the form "[1,2][3,4]" :

  One option is to use split next to regular expressions to build the array from the string.

  import numpy as np
  import re
  
  
  def matrixDet(matrix):
      return np.linalg.det(matrix)
  
  def parse_matriz(cadena):
      # Entrada: una cadena del tipo '[a,b,c][d,f,e]...'
      # Salida una lista de la forma [[a,b,c],[d,e,f]] contruida con los datos de entrada
      cadena = cadena.replace(" ", "")
      return [[float(n) for n in row.split(',')]
                            for row in re.findall("\[(.*?)\]", cadena)]
  
  M2 = input("Ingrese la matriz de la forma [1,2] (esto es una fila), [3,2] (esto es otra fila)")
  M2=parse_matriz(M2)
  print('El determinante es:', matrixDet(M2))
  

  Starting from the fact that the user enters a string of the form '[1,2][3,4]' that may or may not contain spaces, the first thing is to eliminate them with replace(" ", "") . Done this with re.findall("\[(.*?)\]", cadena) we get a list with the rows of the matrix using the brackets as separators: ['1,2', '3,4'] .

  Now we just have to go through each chain of the previous list and separate the numbers using the comma, we pass them to float and put them into a list.

.

• Entry of the form "[[1,2],[3,4]]" :

  Being a string that is valid python code, we can use eval() to pass it directly to a list. However, using eval() for unfiltered user entries is very dangerous and should never be used. What we can use is the secure version ast.literal_eval() :

  import numpy as np
  import ast
  
  
  def matrixDet(matrix):
      return np.linalg.det(matrix)
  
  M2 = ast.literal_eval(input("Ingrese la matriz de la forma [[1,2],[3,4]]: "))
  
  print('El determinante es:', matrixDet(M2))
  

.

Both forms admit spaces between the elements of the matrix and both allow entering both integers and floats. That is, for the first case is valid both [1,2][3,4] as [ 1,2] [3, 4] , same as for the second form.

In both cases it would be appropriate to validate the user's input to avoid exceptions.

Hello to solve this use numpy.matrix () the code stayed like this:

from sympy import *
#from numpy import *
import numpy as np
from matplotlib import *
from py_expression_eval import *
import matplotlib.pyplot as plt
#[1,2] es una fila
#[3,4] otra fila
M = np.matrix('1 2; 3 4')
def matrizDet(matriz):
    matriz = np.matrix(matriz)
    return np.linalg.det(matriz)
M2 = input("Ingrese la matriz de la forma [1, 2] (esto es una fila), [3, 2] (esto es otra fila)")
print(matrizDet(M2))

Now if you read me the data that the user enters but the user must enter them like this: 1, 2; 3, 2 Anyway, if someone knows a way to work with the other way, I appreciate it.