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closure.py
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56 lines (43 loc) · 1.16 KB
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# encoding: utf-8
"""
Topic: sample
Desc :
闭包
"""
__author__ = 'Xiong Neng'
def counter(start_at=0):
count = [start_at] # 使用数组是因为在内部函数内，再对这个变量赋值会报错
def incr():
# count = count + 1 # 这个就是不合法的
count[0] += 1 # 单独count赋值操作是不允许的，但是count[0]赋值是可以的。
return count[0]
return incr
def countdown(n):
def cnext():
nonlocal n # 使用nonlocal可以将变量声明为外部变量了
r = n
n -= 1
return r
return cnext
def magic_closure():
# python中的闭包是后期绑定，运行时绑定
flist = []
for i in range(3):
flist.append(lambda: i)
print([f() for f in flist]) # [2, 2, 2], strange, ha?
flist = []
for i in range(3):
flist.append(lambda x=i: x) # 使用默认参数
print([f() for f in flist]) # [0, 1, 2] cool
def main():
ne = countdown(10)
while True:
v = ne()
print(v)
if not v: break
magic_closure()
aa = 3
if aa <= aa:
pass
if __name__ == '__main__':
main()