cpython/Demo/classes/Vec.py

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class Vec:
""" A simple vector class
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Instances of the Vec class can be constructed from numbers
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>>> a = Vec(1, 2, 3)
>>> b = Vec(3, 2, 1)
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added
>>> a + b
Vec(4, 4, 4)
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subtracted
>>> a - b
Vec(-2, 0, 2)
and multiplied by a scalar on the left
>>> 3.0 * a
Vec(3.0, 6.0, 9.0)
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or on the right
>>> a * 3.0
Vec(3.0, 6.0, 9.0)
"""
def __init__(self, *v):
self.v = list(v)
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@classmethod
def fromlist(cls, v):
if not isinstance(v, list):
raise TypeError
inst = cls()
inst.v = v
return inst
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def __repr__(self):
args = ', '.join(repr(x) for x in self.v)
return 'Vec({0})'.format(args)
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def __len__(self):
return len(self.v)
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def __getitem__(self, i):
return self.v[i]
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def __add__(self, other):
# Element-wise addition
v = [x + y for x, y in zip(self.v, other.v)]
return Vec.fromlist(v)
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def __sub__(self, other):
# Element-wise subtraction
v = [x - y for x, y in zip(self.v, other.v)]
return Vec.fromlist(v)
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def __mul__(self, scalar):
# Multiply by scalar
v = [x * scalar for x in self.v]
return Vec.fromlist(v)
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__rmul__ = __mul__
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def test():
import doctest
doctest.testmod()
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test()