cpython/Tools/demo/vector.py at 3.5 · python/cpython · GitHub

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#!/usr/bin/env python3

"""

A demonstration of classes and their special methods in Python.

"""

class Vec:

"""A simple vector class.

Instances of the Vec class can be constructed from numbers

>>> a = Vec(1, 2, 3)

>>> b = Vec(3, 2, 1)

added

>>> a + b

Vec(4, 4, 4)

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)

or on the right

>>> a * 3.0

Vec(3.0, 6.0, 9.0)

"""

def __init__(self, *v):

self.v = list(v)

@classmethod

def fromlist(cls, v):

if not isinstance(v, list):

raise TypeError

inst = cls()

inst.v = v

return inst

def __repr__(self):

args = ', '.join(repr(x) for x in self.v)

return 'Vec({})'.format(args)

def __len__(self):

return len(self.v)

def __getitem__(self, i):

return self.v[i]

def __add__(self, other):

# Element-wise addition

v = [x + y for x, y in zip(self.v, other.v)]

return Vec.fromlist(v)

def __sub__(self, other):

# Element-wise subtraction

v = [x - y for x, y in zip(self.v, other.v)]

return Vec.fromlist(v)

def __mul__(self, scalar):

# Multiply by scalar

v = [x * scalar for x in self.v]

return Vec.fromlist(v)

__rmul__ = __mul__

def test():

import doctest

doctest.testmod()

test()

cpython/Tools/demo/vector.py at 3.5 · python/cpython · GitHub

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