from array import array
import reprlib
import mathclass Vector:type_code = 'd'def __init__(self,components):self._components = array(self.type_code,components)def __iter__(self):return iter(self._components)def __repr__(self):components = reprlib.repr(self._components)components = components[components.find('['):-1]return 'Vector({})'.format(components)def __str__(self):return str(tuple(self))def __bytes__(self):return bytes([ord(self.type_code)]) + bytes(self._components)def __eq__(self, other):return tuple(self) == tuple(other)def __abs__(self):return math.sqrt(x*x for x in self._components)def __bool__(self):return bool(abs(self))@classmethoddef frombytes(cls,octets):t_code = chr(octets[0])comps = array(t_code)comps.frombytes(octets[1:])return cls(comps)longlist = [i for i in range(100)]
longVector = Vector(longlist)
print('repr(longVector):',repr(longVector))v = Vector([3.1,4.2])
print('str(v):',v)
print('repr(v):',repr(v))
b = bytes(v)
w = Vector.frombytes(b)
print('repr(w):',repr(w))
print(v == w)输出：
repr(longVector): Vector([0.0, 1.0, 2.0, 3.0, 4.0, ...])
str(v): (3.1, 4.2)
repr(v): Vector([3.1, 4.2])
repr(w): Vector([3.1, 4.2])
True

from array import array
import reprlib
import mathclass Vector:type_code = 'd'def __init__(self,components):self._components = array(self.type_code,components)def __iter__(self):return iter(self._components)def __repr__(self):components = reprlib.repr(self._components)components = components[components.find('['):-1]return 'Vector({})'.format(components)def __str__(self):return str(tuple(self))def __bytes__(self):return bytes([ord(self.type_code)]) + bytes(self._components)def __eq__(self, other):return tuple(self) == tuple(other)def __abs__(self):return math.sqrt(x*x for x in self._components)def __bool__(self):return bool(abs(self))@classmethoddef frombytes(cls,octets):t_code = chr(octets[0])comps = array(t_code)comps.frombytes(octets[1:])return cls(comps)# 定义下面两个方法以后，Vector类就支持简单切片def __len__(self):return len(self._components)def __getitem__(self, idx):return self._components[idx]l = [i for i in range(100)]
v = Vector(l)
print('repr(longVector):',repr(v))# []操作符调用__getitem__
print(v[0],v[-1])# _components是一个array，所以切片返回array
print(v[1:4])输出：
repr(longVector): Vector([0.0, 1.0, 2.0, 3.0, 4.0, ...])
0.0 99.0
array('d', [1.0, 2.0, 3.0])

class MySeq:def __getitem__(self, item):return items = MySeq()
l = [1,2,3,4,5]# 切片时传递给__getitem__的参数是slice对象
# 这里是slice(1, 4, None)
print(s[1:4])# slice(1, 4, 2)
print(s[1:4:2])# 在内置可迭代对象的__getitem__中，还要调用indices方法对start、stop、stride进行处理
# 步幅为正数，start=None自动替换成0
# stop超过len，自动替换成len
# (0, 5, 2)
print(slice(None, 10, 2).indices(5))
# 相应切片返回[1, 3, 5]
print(l[:10:2])# 步幅=None，自动替换成1
# 步幅为正数，start=-3自动替换成len-3
# stop=None自动替换成len
# (2, 5, 1)
print(slice(-3, None, None).indices(5))
# 相应切片返回[3, 4, 5]
print(l[-3::])# 步幅为负数，start=-3自动替换成len-3
# stop=None自动替换成-1
# (2, -1, -1)
print(slice(-3, None, -1).indices(5))
# 相应切片返回[3, 2, 1]
print(l[-3::-1])# 从2开始，倒退到3，切片为空
# (2, 3, -1)
print(slice(-3, 3, -1).indices(5))
# 相应切片返回[]
print(l[-3:3:-1])

from array import array
import reprlib
import math
import numbersclass Vector:type_code = 'd'def __init__(self,components):self._components = array(self.type_code,components)def __iter__(self):return iter(self._components)def __repr__(self):components = reprlib.repr(self._components)components = components[components.find('['):-1]return 'Vector({})'.format(components)def __str__(self):return str(tuple(self))def __bytes__(self):return bytes([ord(self.type_code)]) + bytes(self._components)def __eq__(self, other):return tuple(self) == tuple(other)def __abs__(self):return math.sqrt(x*x for x in self._components)def __bool__(self):return bool(abs(self))@classmethoddef frombytes(cls,octets):t_code = chr(octets[0])comps = array(t_code)comps.frombytes(octets[1:])return cls(comps)# 定义下面两个方法以后，Vector类就支持简单切片def __len__(self):return len(self._components)def __getitem__(self, idx):cls = type(self)if isinstance(idx,slice):# 把slice对象传递给_components的__getitem__函数return cls(self._components[idx])elif isinstance(idx,numbers.Integral):# 直接返回相应元素return self._components[idx]else:msg = '{0} indices must be integers'raise TypeError(msg.format(cls.__name__))l = [i for i in range(100)]
v = Vector(l)
print('repr(longVector):',repr(v))# 传入整数，__getitem__返回相应元素
print(v[0],v[-1])# 经过改造后，切片返回Vector对象
print(repr(v[1:4]))

from array import array
import reprlib
import math
import numbers
import functools
import operatorclass Vector:type_code = 'd'def __init__(self,components):self._components = array(self.type_code,components)def __iter__(self):return iter(self._components)def __repr__(self):components = reprlib.repr(self._components)components = components[components.find('['):-1]return 'Vector({})'.format(components)def __str__(self):return str(tuple(self))def __bytes__(self):return bytes([ord(self.type_code)]) + bytes(self._components)def __eq__(self, other):# zip生成一个由元组构成的生成器，在Vector由大数据量的可迭代对象构成时，效率比较高# all函数在每一个元素都为True时返回Truereturn len(self)==len(other) and all(a==b for a,b in zip(self,other))def __hash__(self):# reduce接受三个参数，第一个参数是一个可接受两个参数的函数# 第二个参数是一个可迭代对象，第三个参数是初始值，如果可迭代对象为空，返回这个初始值hashes = (hash(i) for i in self)return functools.reduce(operator.xor, hashes, 0)def __abs__(self):return math.sqrt(x*x for x in self._components)def __bool__(self):return bool(abs(self))@classmethoddef frombytes(cls,octets):t_code = chr(octets[0])comps = array(t_code)comps.frombytes(octets[1:])return cls(comps)# 定义下面两个方法以后，Vector类就支持简单切片def __len__(self):return len(self._components)def __getitem__(self, idx):cls = type(self)if isinstance(idx,slice):# 把slice对象传递给_components的__getitem__函数return cls(self._components[idx])elif isinstance(idx,numbers.Integral):# 直接返回相应元素return self._components[idx]else:msg = '{0} indices must be integers'raise TypeError(msg.format(cls.__name__))shortcut = 'xyzt'# 动态存取属性def __getattr__(self, item):cls = type(self)if len(item) == 1:pos = cls.shortcut.find(item)if 0 <= pos < len(self._components):return self._components[pos]else:raise AttributeError('{0} has no attribute {1}'.format(cls,item))l = [3.1, 4.2]
v = Vector(l)
print('repr(v):',repr(v))print('v.x:',v.x)print('hash(v):',hash(v))

输出：

repr(v): Vector([3.1, 4.2])
v.x: 3.1
hash(v): 384307168202284039