coderjack
diff --git a/‎matrix/matrix_class.py‎
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+# An OOP aproach to representing and manipulating matrices
+
+
+class Matrix:
+    """
+    Matrix object generated from a 2D array where each element is an array representing a row.
+    Rows can contain type int or float.
+    Common operations and information available.
+    >>> rows = [
+    ...     [1, 2, 3],
+    ...     [4, 5, 6],
+    ...     [7, 8, 9]
+    ... ]
+    >>> matrix = Matrix(rows)
+    >>> print(matrix)
+    [[1. 2. 3.]
+     [4. 5. 6.]
+     [7. 8. 9.]]
+    
+    Matrix rows and columns are available as 2D arrays
+    >>> print(matrix.rows)
+    [[1, 2, 3], [4, 5, 6], [7, 8, 9]]
+    >>> print(matrix.columns())
+    [[1, 4, 7], [2, 5, 8], [3, 6, 9]]
+    
+    Order is returned as a tuple
+    >>> matrix.order
+    (3, 3)
+
+    Squareness and invertability are represented as bool
+    >>> matrix.is_square
+    True
+    >>> matrix.is_invertable()
+    False
+
+    Identity, Minors, Cofactors and Adjugate are returned as Matrices.  Inverse can be a Matrix or Nonetype
+    >>> print(matrix.identity())
+    [[1. 0. 0.]
+     [0. 1. 0.]
+     [0. 0. 1.]]
+    >>> print(matrix.minors())
+    [[-3. -6. -3.]
+     [-6. -12. -6.]
+     [-3. -6. -3.]]
+    >>> print(matrix.cofactors())
+    [[-3. 6. -3.]
+     [6. -12. 6.]
+     [-3. 6. -3.]]
+    >>> print(matrix.adjugate()) # won't be apparent due to the nature of the cofactor matrix
+    [[-3. 6. -3.]
+     [6. -12. 6.]
+     [-3. 6. -3.]]
+    >>> print(matrix.inverse())
+    None
+
+    Determinant is an int, float, or Nonetype
+    >>> matrix.determinant()
+    0
+
+    Negation, scalar multiplication, addition, subtraction, multiplication and exponentiation are available and all return a Matrix
+    >>> print(-matrix)
+    [[-1. -2. -3.]
+     [-4. -5. -6.]
+     [-7. -8. -9.]]
+    >>> matrix2 = matrix * 3
+    >>> print(matrix2)
+    [[3. 6. 9.]
+     [12. 15. 18.]
+     [21. 24. 27.]]
+    >>> print(matrix + matrix2)
+    [[4. 8. 12.]
+     [16. 20. 24.]
+     [28. 32. 36.]]
+    >>> print(matrix - matrix2)
+    [[-2. -4. -6.]
+     [-8. -10. -12.]
+     [-14. -16. -18.]]
+    >>> print(matrix ** 3)
+    [[468. 576. 684.]
+     [1062. 1305. 1548.]
+     [1656. 2034. 2412.]]
+
+    Matrices can also be modified
+    >>> matrix.add_row([10, 11, 12])
+    >>> print(matrix)
+    [[1. 2. 3.]
+     [4. 5. 6.]
+     [7. 8. 9.]
+     [10. 11. 12.]]
+    >>> matrix2.add_column([8, 16, 32])
+    >>> print(matrix2)
+    [[3. 6. 9. 8.]
+     [12. 15. 18. 16.]
+     [21. 24. 27. 32.]]
+    >>> print(matrix *  matrix2)
+    [[90. 108. 126. 136.]
+     [198. 243. 288. 304.]
+     [306. 378. 450. 472.]
+     [414. 513. 612. 640.]]
+
+    """
+
+    def __init__(self, rows):
+        error = TypeError(
+            "Matrices must be formed from a list of zero or more lists containing at least one and the same number of values, \
+                each of which must be of type int or float"
+        )
+        if len(rows) != 0:
+            cols = len(rows[0])
+            if cols == 0:
+                raise error
+            for row in rows:
+                if not len(row) == cols:
+                    raise error
+                for value in row:
+                    if not isinstance(value, (int, float)):
+                        raise error
+            self.rows = rows
+        else:
+            self.rows = []
+
+    # MATRIX INFORMATION
+    def columns(self):
+        return [[row[i] for row in self.rows] for i in range(len(self.rows[0]))]
+
+    @property
+    def num_rows(self):
+        return len(self.rows)
+
+    @property
+    def num_columns(self):
+        return len(self.rows[0])
+
+    @property
+    def order(self):
+        return (self.num_rows, self.num_columns)
+
+    @property
+    def is_square(self):
+        if self.order[0] == self.order[1]:
+            return True
+        return False
+
+    def identity(self):
+        values = [
+            [0 if column_num != row_num else 1 for column_num in range(self.num_rows)]
+            for row_num in range(self.num_rows)
+        ]
+        return Matrix(values)
+
+    def determinant(self):
+        if not self.is_square:
+            return None
+        if self.order == (0, 0):
+            return 1
+        if self.order == (1, 1):
+            return self.rows[0][0]
+        if self.order == (2, 2):
+            return (self.rows[0][0] * self.rows[1][1]) - (
+                self.rows[0][1] * self.rows[1][0]
+            )
+        else:
+            return sum(
+                [
+                    self.rows[0][column] * self.cofactors().rows[0][column]
+                    for column in range(self.num_columns)
+                ]
+            )
+
+    def is_invertable(self):
+        if self.determinant():
+            return True
+        return False
+
+    def get_minor(self, row, column):
+        values = [
+            [
+                self.rows[other_row][other_column]
+                for other_column in range(self.num_columns)
+                if other_column != column
+            ]
+            for other_row in range(self.num_rows)
+            if other_row != row
+        ]
+        return Matrix(values).determinant()
+
+    def get_cofactor(self, row, column):
+        if (row + column) % 2 == 0:
+            return self.get_minor(row, column)
+        return -1 * self.get_minor(row, column)
+
+    def minors(self):
+        return Matrix(
+            [
+                [self.get_minor(row, column) for column in range(self.num_columns)]
+                for row in range(self.num_rows)
+            ]
+        )
+
+    def cofactors(self):
+        return Matrix(
+            [
+                [
+                    self.minors().rows[row][column]
+                    if (row + column) % 2 == 0
+                    else self.minors().rows[row][column] * -1
+                    for column in range(self.minors().num_columns)
+                ]
+                for row in range(self.minors().num_rows)
+            ]
+        )
+
+    def adjugate(self):
+        values = [
+            [self.cofactors().rows[column][row] for column in range(self.num_columns)]
+            for row in range(self.num_rows)
+        ]
+        return Matrix(values)
+
+    def inverse(self):
+        if not self.is_invertable():
+            return None
+        return self.adjugate() * (1 / self.determinant())
+
+    def __repr__(self):
+        return str(self.rows)
+
+    def __str__(self):
+        if self.num_rows == 0:
+            return "[]"
+        if self.num_rows == 1:
+            return "[[" + ". ".join(self.rows[0]) + "]]"
+        return (
+            "["
+            + "\n ".join(
+                [
+                    "[" + ". ".join([str(value) for value in row]) + ".]"
+                    for row in self.rows
+                ]
+            )
+            + "]"
+        )
+
+    # MATRIX MANIPULATION
+    def add_row(self, row, position=None):
+        type_error = TypeError("Row must be a list containing all ints and/or floats")
+        if not isinstance(row, list):
+            raise type_error
+        for value in row:
+            if not isinstance(value, (int, float)):
+                raise type_error
+        if len(row) != self.num_columns:
+            raise ValueError(
+                "Row must be equal in length to the other rows in the matrix"
+            )
+        if position is None:
+            self.rows.append(row)
+        else:
+            self.rows = self.rows[0:position] + [row] + self.rows[position:]
+
+    def add_column(self, column, position=None):
+        type_error = TypeError(
+            "Column must be a list containing all ints and/or floats"
+        )
+        if not isinstance(column, list):
+            raise type_error
+        for value in column:
+            if not isinstance(value, (int, float)):
+                raise type_error
+        if len(column) != self.num_rows:
+            raise ValueError(
+                "Column must be equal in length to the other columns in the matrix"
+            )
+        if position is None:
+            self.rows = [self.rows[i] + [column[i]] for i in range(self.num_rows)]
+        else:
+            self.rows = [
+                self.rows[i][0:position] + [column[i]] + self.rows[i][position:]
+                for i in range(self.num_rows)
+            ]
+
+    # MATRIX OPERATIONS
+    def __eq__(self, other):
+        if not isinstance(other, Matrix):
+            raise TypeError("A Matrix can only be compared with another Matrix")
+        if self.rows == other.rows:
+            return True
+        return False
+
+    def __ne__(self, other):
+        if self == other:
+            return False
+        return True
+
+    def __neg__(self):
+        return self * -1
+
+    def __add__(self, other):
+        if self.order != other.order:
+            raise ValueError("Addition requires matrices of the same order")
+        return Matrix(
+            [
+                [self.rows[i][j] + other.rows[i][j] for j in range(self.num_columns)]
+                for i in range(self.num_rows)
+            ]
+        )
+
+    def __sub__(self, other):
+        if self.order != other.order:
+            raise ValueError("Subtraction requires matrices of the same order")
+        return Matrix(
+            [
+                [self.rows[i][j] - other.rows[i][j] for j in range(self.num_columns)]
+                for i in range(self.num_rows)
+            ]
+        )
+
+    def __mul__(self, other):
+        if not isinstance(other, (int, float, Matrix)):
+            raise TypeError(
+                "A Matrix can only be multiplied by an int, float, or another matrix"
+            )
+        if type(other) in (int, float):
+            return Matrix([[element * other for element in row] for row in self.rows])
+        if type(other) is Matrix:
+            if self.num_columns != other.num_rows:
+                raise ValueError(
+                    "The number of columns in the first matrix must be equal to the number of rows in the second"
+                )
+            return Matrix(
+                [
+                    [Matrix.dot_product(row, column) for column in other.columns()]
+                    for row in self.rows
+                ]
+            )
+
+    def __pow__(self, other):
+        if not isinstance(other, int):
+            raise TypeError("A Matrix can only be raised to the power of an int")
+        if not self.is_square:
+            raise ValueError("Only square matrices can be raised to a power")
+        if other == 0:
+            return self.identity()
+        if other < 0:
+            if self.is_invertable:
+                return self.inverse() ** (-other)
+            raise ValueError(
+                "Only invertable matrices can be raised to a negative power"
+            )
+        result = self
+        for i in range(other - 1):
+            result *= self
+        return result
+
+    @classmethod
+    def dot_product(cls, row, column):
+        return sum([row[i] * column[i] for i in range(len(row))])
+
+
+if __name__ == "__main__":
+    import doctest
+
+    test = doctest.testmod()
+    print(test)