50 lines
2.0 KiB
Python
50 lines
2.0 KiB
Python
import copy
|
|
|
|
class Matrix(object):
|
|
"""
|
|
Matrix class with some basic matrix operations
|
|
"""
|
|
def __init__(self, array):
|
|
columns = len(array[0])
|
|
for r in array[1:]: #make sure each row has same number of columns
|
|
assert len(r) == columns
|
|
|
|
self.array = copy.copy(array)
|
|
self.rows = len(array)
|
|
self.columns = columns
|
|
|
|
def __repr__(self):
|
|
return self.__str__()
|
|
|
|
def __str__(self):
|
|
a = ['[' + ', '.join([str(i) for i in r]) + ']' for r in self.array]
|
|
return '[\n' + ',\n'.join(a) + '\n]'
|
|
|
|
def minor(self, row, col):
|
|
return Matrix([[self[r][c] for c in range(self.columns) if c != col] for r in range(self.rows) if r != row])
|
|
|
|
def det(self):
|
|
if self.rows != self.columns:
|
|
raise TypeError, 'Can only calculate determinant for a square matrix'
|
|
if self.rows == 1:
|
|
return self[0][0]
|
|
if self.rows == 2:
|
|
return self[0][0] * self[1][1] - self[0][1] * self[1][0]
|
|
det = 0
|
|
for i in range(self.columns):
|
|
det += (-1)**i * self.array[0][i] * self.minor(0, i).det()
|
|
return det
|
|
|
|
def __getitem__(self, index):
|
|
return self.array[index]
|
|
|
|
def __add__(self, other):
|
|
if self.rows != other.rows or self.columns != other.columns:
|
|
raise TypeError, 'Both matrices should have equal dimensions. Is ({} x {}) and ({} x {}).'.format(self.rows, self.columns, other.rows, other.columns)
|
|
return Matrix([[self[r][c] + other[r][c] for c in range(self.columns)] for r in range(self.rows)])
|
|
|
|
def __mul__(self, other):
|
|
if self.columns != other.rows:
|
|
raise TypeError, 'Left matrix should have same number of columns as right matrix has rows. Is ({} x {}) and ({} x {}).'.format(self.rows, self.columns, other.rows, other.columns)
|
|
return Matrix([[sum([self[r][i] * other[i][c] for i in range(self.columns)]) for c in range(other.columns)] for r in range(self.rows)])
|