Is there a way to use __str__ in a class but returning a list?

Question

When I call a class object, I want it to return a list or any other variable other than string

class Vec:
    def __init__(self, data) -> None:
        self.data = data #THIS IS A LIST

    def __str__(self) -> list:
        return self.data

a = Vec([0,1,2,3])
print(a) 

#TypeError: __str__ returned non-string (type list)

Instead I get a TypeError, if I set the "self.data" to a string it will work

Is there any Magic Method for this? Thanks in advance

here is the full code in case you need to see it all

note: I am not done finishing it yet and my problem is that for example if I want to multiply Mat with a Vec I would have to do Mat * Vec.data or Mat * Vec.T (T stands for transposed) which I dont like and I would just like to type Mat * Vec in case I dont need to transpose the vector. Sorry for my messy code and my bad explanation of my problem

class MatrixMatchError(Exception):
    def __init__(self):
        self.message = "Matrix sizes do not match"
        super().__init__(self.message)
    pass

class MatrixRowColError(Exception):
    def __init__(self):
        self.message = "The number of columns in the first matrix do not equal to the number of rows in the second."
        super().__init__(self.message)
    pass

class Vec:
    def __init__(self, x, identity=1) -> None:
        self.x = x
        self.data = self.Create(x, 1, identity)
        self.T = self.Transpose()

    def Create(self, x, y, identity) -> list:
        vec = []
        for i in range(y):
            vec.append([])
            for j in range(x):
                vec[i].append(identity)

        return vec

    def Transpose(self) -> list:
        vec = self.Create(len(self.data), len(self.data[0]), 0)
        for i in range(len(self.data)):
            for j in range(len(self.data[0])):
                vec[j][i] = self.data[i][j]

        return vec

class Mat:
    def __init__(self, x, y=0, identity=1) -> None:
        self.x = x
        if y == 0:
            self.y = x
        else:
            self.y = y

        self.data = self.Create(self.x, self.y, identity)
        self.T = self.Transpose()

    def __add__(self, data):
        if not self.CheckSize(data):
            raise MatrixMatchError

        mat3 = self.data.copy()
        for i in range(len(self.data)):
            for j in range(len(self.data[0])):
                mat3[i][j] = self.data[i][j] + data[i][j]

        return mat3

    def __sub__(self, data):
        if not self.CheckSize(data):
            raise MatrixMatchError

        mat3 = self.data.copy()
        for i in range(len(self.data)):
            for j in range(len(self.data[0])):
                mat3[i][j] = self.data[i][j] - data[i][j]

        return mat3

    def __mul__(self, data):
        if not self.CheckRowCol(data):
            raise MatrixRowColError

        mat3 = self.Create(len(data[0]), len(self.data),  0)

        for i in range(len(self.data)):
            for j in range(len(data[0])):
                for k in range(len(self.data[0])):
                    mat3[i][j] += self.data[i][k] * data[k][j]

        return mat3

    def Create(self, x, y, identity) -> list:
        mat = []
        for i in range(y):
            mat.append([])
            for j in range(x):
                mat[i].append(0)

        if x == y:
            for i in range(x):
                mat[i][i] = identity

        return mat

    def Transpose(self) -> list:
        mat = self.Create(len(self.data), len(self.data[0]), 0)
        for i in range(len(self.data)):
            for j in range(len(self.data[0])):
                mat[j][i] = self.data[i][j]

        return mat

    def CheckSize(self, data):
        if len(self.data) != len(data) or len(self.data[0]) != len(data[0]):
            return False
        return True

    def CheckRowCol(self, data):
        if len(data) != len(self.data[0]):
            return False
        return True

    def Transform(self):
        pass

    def Scale(self):
        pass

    def Rotate(self):
        pass
        

mat1 = Mat(2)
mat1.data = [[4,5, 4],
            [9,3, 7],
            [7,1, 3]]

vec = Vec(3)
print(mat1 * vec.T)