问题
Possible Duplicate:
Lexical closures in Python
Suppose I have the following code
callbacks = []
for i in range(10):
callbacks.append(lambda x: i)
all functions in callbacks will return the final value of i. How can I create callbacks that return the current value for i at creation time?
回答1:
for i in range(10):
callbacks.append(lambda x = i : x)
回答2:
In [113]: callbacks=[]
In [114]: for i in range(10):
callbacks.append(lambda x=i:x**2)
.....:
.....:
In [117]: callbacks[0]()
Out[117]: 0
In [118]: callbacks[1]()
Out[118]: 1
In [119]: callbacks[2]()
Out[119]: 4
In [120]: callbacks[4]()
Out[120]: 16
来源：https://stackoverflow.com/questions/13038779/closures-and-loops-in-python