我的代码中的 Python“回溯错误”，不确定如何解决

Question

Good evening StackOverflow users! I'm working on a python code that does the following:

the user will enter values of two, 3x3 matrices and then select from options including, addition, subtraction, matrix multiplication, and element by element multiplication. You should use numpy.matmul() for matrix multiplication (eg np.matmul(a, b) ). The program should compute the appropriate results and return the results, the transpose of the results, the mean of the rows for the results, and the mean of the columns for the results

However, the code as I have it, produces an error message as follows.

Traceback (most recent call last):
  File "C:/Users/jwhoc/OneDrive/Documents/Python Tests/week4_lab.py", line 40, in <module>
    print(a[i][j],end=" ")
IndexError: list index out of range

This error message occurs after you enter your 3x3 matrix the first time. I'll insert the code below.

import numpy as np
import re
print("*******************************Welcome to the Python Matrix Application*******************")
while True:
    print("Do you want to play the Matrix Game?")
    #Reading the choice
    choice=input("Enter Y for yes or N for No:")
    if choice=="N":
        print("****************Thanks for playing Python Numpy************************")
        break
    else:
        while True:
            phone=input("Enter your phone number(XXX-XXX-XXXX):")
            #Regular expression for checking the phone number format
            if not re.match("\d{3}-\d{3}-\d{4}",phone):
                print("Your phone number is not in correct format. Please reenter:")
            else:
                break
        while True:
            zip=input("Enter your zipcode+4(XXXXX-XXXX):")
            #Regular expression for checking the zipcode format
            if not re.match("\d{5}-\d{4}",zip):
                print("Your zipcode is not in correct format. Please reenter:")
            else:
                break
        #Reading the first matrix
        print("Enter your first 3x3 matrix:")
        a=[]
        for i in range(3):
            #Reading row by row
            row=input().split()
            #Converting each element to integer
            row=list(map(int,row))
            #Adding row to the matrix
            a.append(row)
        #Printing first matrix
        print("Your first 3x3 matrix is:")
        for i in range(3):
            for j in range(3):
                print(a[i][j],end=" ")
            print()

Any help you all can give would be fantastic. Thanks guys!

Answer 1

I run your code and it works perfectly, but I think the problem that you may had was the form that you introduce your inputs. For example: If you provide the rows in this way there's no problem:

2 5 6

But if you did it like this:

256

You will get the same error that you say, that's because when your calling

row = input().split()

you are not getting [2, 5, 6] , but [256] instead. That's because the default separator of split() function is a space. In case you want to introduce the values in this way 256 , you should change row = input().split() to

row = input().split("")

Note that there's not space in ""

Answer 2

The issue is that matrics input does conform the required format. str.split() splits on the " " character unless otherwise specified so numbers must be separated by spaces. I think it might be helpful to do some error checking on the matrix inputs similarly to earlier inputs. Try this out:

import re
print("*******************************Welcome to the Python Matrix Application*******************")
while True:
    print("Do you want to play the Matrix Game?")
    #Reading the choice
    choice=input("Enter Y for yes or N for No:")
    if choice=="N":
        print("****************Thanks for playing Python Numpy************************")
        break
    else:
        while True:
            phone=input("Enter your phone number(XXX-XXX-XXXX):")
            #Regular expression for checking the phone number format
            if not re.match("\d{3}-\d{3}-\d{4}",phone):
                print("Your phone number is not in correct format. Please reenter:")
            else:
                break
        while True:
            zip=input("Enter your zipcode+4(XXXXX-XXXX):")
            #Regular expression for checking the zipcode format
            if not re.match("\d{5}-\d{4}",zip):
                print("Your zipcode is not in correct format. Please reenter:")
            else:
                break
        #Reading the first matrix
        print("Enter your first 3x3 matrix:")
        a=[]
        for i in range(3):
            while True
                #Reading row by row
                row=input().split()
                #Converting each element to integer
                row=list(map(int,row))
                if len(row) != 3:
                    print(f"Needs 3 numbers. {len(row)} numbers specified. Please re-enter:")
                else:
                    break
            #Adding row to the matrix
            a.append(row)
        #Printing first matrix
        print("Your first 3x3 matrix is:")
        for i in range(3):
            for j in range(3):
                print(a[i][j],end=" ")
            print()