實例講解Python的函數閉包使用中應注意的問題

from functools import wraps
from time import sleep

def retry(attempts=3, wait=2):
 if attempts < 0 or attempts > 5:
 retry_times = 3
 else:
 retry_times = attempts
 if wait < 0 or wait > 5:
 retry_wait = 2
 else:
 retry_wait = after
 def retry_decorator(func):
 @wraps(func)
 def wrapped_function(*args, **kwargs):
 while retry_times > 0:
 try:
 return func(*args, **kwargs)
 except :
 sleep(retry_wait)
 retry_times -= 1
 return wrapped_function
 return retry_decorator

@retry(7, 8)
def test():
 print 23333
 raise Exception('Call me exception 2333.')

if __name__ == '__main__':
 test()

output: UnboundLocalError: local variable 'retry_times' referenced before assignment

def retry(attempts=3, wait=2):
 temp_dict = {
 'retry_times': 3 if attempts < 0 or attempts > 5 else attempts,
 'retry_wait': 2 if wait < 0 or wait > 5 else wait
 }

 def retry_decorate(fn):
 @wraps(fn)
 def wrapped_function(*args, **kwargs):
 print id(temp_dict), temp_dict
 while temp_dict.get('retry_times') > 0:
 try:
 return fn(*args, **kwargs)
 except :
 sleep(temp_dict.get('retry_wait'))
 temp_dict['retry_times'] = temp_dict.get('retry_times') - 1
 print id(temp_dict), temp_dict

 print id(temp_dict), temp_dict

 return wrapped_function

 return retry_decorate

@retry(7, 8)
def test():
 print 23333
 raise Exception('Call me exception 2333.')

if __name__ == '__main__':
 test()

4405472064 {'retry_wait': 2, 'retry_times': 3}
4405472064 {'retry_wait': 2, 'retry_times': 3}
23333
4405472064 {'retry_wait': 2, 'retry_times': 2}
23333
4405472064 {'retry_wait': 2, 'retry_times': 1}
23333
4405472064 {'retry_wait': 2, 'retry_times': 0}

>>> test.func_closure[1].cell_contents
{'retry_wait': 2, 'retry_times': 2}