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Python 中的闭包以一种“奇怪”的方式表现，可以这么说。考虑以下代码片段，其中我尝试基于foo两种方式构建闭包列表： 在bad_closure中，闭包是“动态”构建的，而在good_closure闭包中是由辅助函数构建的：

def foo(d):
    return d + 1

def bad_closure():
    ''' shares resources implicitly '''

    # list of 5 closures
    # `i` is shared between all closures
    cls = [lambda : foo(i) for i in range(5)]
    return cls

def good_closure():
    ''' no resource sharing '''

    def mk_cl(i):
        ''' helper to make a closure'''
        c_ = lambda : foo(i)
        return c_

    # list of 5 closures
    # each closure has its own `i`
    cls = [mk_cl(i) for i in range(5)]
    return cls

#--- TEST ---
bs = bad_closure()
print([f() for f in bs]) # output: [5, 5, 5, 5, 5]

gs = good_closure()
print([f() for f in gs]) # output: [1, 2, 3, 4, 5]

结果惊人地不同。似乎在 中bad_closure，闭包每个都有一个固定值 i，但它们都共享相同 的i内容，每次迭代都会更新（最后取值5）！相反， in good_closure,i是分开的——正如我所料。

我想看看幕后发生了什么以及为什么。

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