matrix_transpose.py

class Matrix:
    """Interface of a matrix.

    This class provides only the matrix size N and a method for swapping
    two items. The actual storage of the matrix in memory is provided by
    subclasses in testing code.
    """

    def __init__(self, N):
        self.N = N

    def swap(self, i1, j1, i2, j2):
        """Swap elements (i1,j1) and (i2,j2)."""

        # Overridden in subclasses
        raise NotImplementedError

    def transpose(self):
        """Transpose the matrix."""

        # TODO: Implement more efficiently
        for i in range(self.N):
            for j in range(i):
                self.swap(i, j, j, i)