Python closures: function defined inside of function can access variables one level above? -


i'm learning decorators, , have question. in decorator function call_counter, function defined , returned, , "replace" function func passed in parameter decorator function. 

def call_counter(func):     def helper(*args, **kwargs):         helper.calls += 1         return func(*args, **kwargs)      helper.calls = 0      return helper

once done, can access helper.calls outside function in manner:

@call_counter def addition(x, y):     return x + y  print(addition.calls) addition(1, 2) print(addition.calls)

the output:

0 1

my question is, how can helper.calls variable exist in memory after call_counter function has been called , exited? far understand, helper.calls exists in call_counter's memory. seems unlikely if variable can accessed after execution of call_counter finished.

calls property of helper , live until helper dies, , helper not going die because, said, live under addition name.


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