69 lines
1.7 KiB
Python
69 lines
1.7 KiB
Python
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# 我们有时候可以用函数来拓展闭包，使闭包获得类似类的效果
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def sample():
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n = 0
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def func():
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print("n=", n)
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def get_n():
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return n
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def set_n(value):
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# nonlocal让我们可以访问闭包内的变量，有点类似类里的self
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nonlocal n
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n = value
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# 我们能这么做的本质原因还是因为Python里的万物皆类特性
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func.get_n = get_n
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func.set_n = set_n
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return func
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f = sample()
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f()
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# 可以看到这里并没有出现代码提示，因为基类没有包含这些东西，它们是在动态编译的时候加入的
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f.set_n(10)
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f()
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f.get_n()
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import sys
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# 比如下面有个类
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class ClosureInstance:
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def __init__(self, locals=None):
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if locals is None:
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locals = sys._getframe(1).f_locals
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self.__dict__.update((key, value) for key, value in locals.items() if callable(value))
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def __len__(self):
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return self.__dict__['__len__']()
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# 这是用这个类实现的栈实例
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def Stack():
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items = []
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def push(item):
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items.append(item)
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def pop():
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items.pop()
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def __len__():
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return len(items)
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return ClosureInstance()
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# 这是正常的写法
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class Stack2:
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def __init__(self):
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self.items = []
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def push(self, item):
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self.items.append(item)
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def pop(self):
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return self.items.pop()
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def __len__(self):
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return len(self.items)
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# 从执行来说，闭包的写法比正常写法块8%，因为不需要访问额外的self变量
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# 不!要!这!么!做!除非有非得这样干的理由,否则别这样搞,老老实实写类,这样的闭包只有类的功能而没有继承多态这些类属性
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