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