摘要：
a={}result=a.setdefault("e")#return None and a add a new key-value pairprint a#a={"e":None}result-a.setdefault("e","eeee")#return None,because the dict already has "e" element so it return current "e"... 阅读全文
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摘要：
a={}result=a.setdefault("e")#return None and a add a new key-value pairprint a#a={"e":None}result-a.setdefault("e","eeee")#return None,because the dict already has "e" element so it return current "e"... 阅读全文
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