Python Forum

So our assignment is to ask for user input for two matrices and then multiply them and show the result then switch the result to a transpose. Since I did it in 1D instead of 2D, I have to transpose the original A and B rather than C. So how can I do this? This is what I have so far and all of this works as intended. Just need help with the transposing part:

Ar, Ac = input("Enter matrix A rows and columns: ").split()
Br, Bc = input("Enter matrix B rows and columns: ").split()
A = input("Enter matrix A: ").split()
B = input("Enter matrix B: ").split()

intAr, intAc = int(Ar), int(Ac)
intBr, intBc = int(Br), int(Bc)
AMatrix = list()
BMatrix = list()
CMatrix = list()

if Ac == Br:
    print(f"\nMatrix A:")
    for x in range(intAr):
        AList = list()
        for y in range(intAc):
            AList.append(int(A[y + intAc*x]))
            print(str(A[y+intAc*x])," ", end = '')
        AMatrix.append(AList)
        print()
    print(f"\nMatrix B:")
    for x in range(intBr):
        BList = list()
        for y in range(intBc):
            BList.append(int(B[y + intBc*x]))
            print(str(B[y+intBc*x])," ", end = '')
        BMatrix.append(BList)
        print()
    print(f"\nMatrix C:")
    for x in range(intAr):
        for y in range(intBc):
            C = 0
            for z in range(intBr):
                C += (AMatrix[x][z] * BMatrix[z][y])
            CMatrix.append(C)
            print(C, ' ', end ='')
        print()
    print(f"\nTranspose matrix T:")  
else:
    print(f"\nCannot be multiplied. Please make sure the number of columns of A and rows of B are the same.")

It's incredibly simple to transpose a 2D matrix in Python:

transposed = zip(*matrix)

It's so simple, that if you are working in 1D, I would suggest converting to 2D to do the transposition.

(Mar-01-2019, 10:46 PM)ichabod801 Wrote: [ -> ]It's incredibly simple to transpose a 2D matrix in Python:

transposed = zip(*matrix)

It's so simple, that if you are working in 1D, I would suggest converting to 2D to do the transposition.

How can I convert the C Matrix into a 2D Matrix though? Sorry, this is my first semester ever in compsci so I am so lost right now.

Well, looking at your code, you are actually working in 2D. Your matrices are stored as a list of lists. So you can just use the code I showed you. Note that it will give you a generator, not a list, but you can fix that by doing transposed = list(zip(*matrix))

The reason it works is that zip takes any number of lists as parameters. It then returns a list of the first item in each list, a list of the second item in each list, a list of the third item in each list, and so on. The star (*) notation converts a sequence (like a list) into a series of parameters.

(Mar-02-2019, 06:55 PM)ichabod801 Wrote: [ -> ]Well, looking at your code, you are actually working in 2D. Your matrices are stored as a list of lists. So you can just use the code I showed you. Note that it will give you a generator, not a list, but you can fix that by doing transposed = list(zip(*matrix))

The reason it works is that zip takes any number of lists as parameters. It then returns a list of the first item in each list, a list of the second item in each list, a list of the third item in each list, and so on. The star (*) notation converts a sequence (like a list) into a series of parameters.

Oh. So just simply use the code? But it's a library function isn't it... We aren't allowed to use those for now :(
And the code didn't work...

It's a built-in function, just like list, int, range, and input.

You could write a set of loops to do what I described: get a list of the first item in each list, a list of the second item in each list, a list of the third item in each list, and so on. But you would have to loop through the indexes of the list and the sub-lists, which wouldn't be very Pythonic.