问题描述
请说明rong_aggregator与聚合器有何不同。即使在aggr = {}之后,agrg仍如何保持其值?我使用Python 3.7进行了测试。
在对任何一个聚合器进行3次调用之后,aggr的预期内容为:
{'a': ['apple','apple','apple'],'b': ['banana','banana','banana'],'c': ['chery','chery','chery']}
def result_gen():
return {'a':'apple','b':'banana','c':'chery'}
def aggregator(results,aggr):
for k,v in results.items():
if k not in aggr:
aggr[k] = []
aggr[k].append(v)
def wrong_aggregator(results,aggr = {}):
for k,v in results.items():
if k not in aggr:
aggr[k] = []
aggr[k].append(v)
return aggr
def test():
aggr = wrong_aggregator(result_gen())
aggr = wrong_aggregator(result_gen(),aggr)
aggr = wrong_aggregator(result_gen(),aggr)
print(len(aggr['a'])) # 3 as expected
#aggr = {} # this line has no effect
aggr = wrong_aggregator(result_gen()) # expected to reset aggr
aggr = wrong_aggregator(result_gen(),aggr)
# !!!!
print(len(aggr['a'])) # 6 instead of 3,aggr was not reset
# this works as expected
aggr2 = {}
aggregator(result_gen(),aggr2)
aggregator(result_gen(),aggr2)
print(len(aggr2['a'])) # 3,OK
aggr2 = {}
aggregator(result_gen(),OK
test()```
Thanks.
解决方法
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