在 2016年10月22日星期六 UTC+8下午5:06:22，Frank Millman写道： > wrote in message > news:2853d778-857e-46fc-96a0-8d164c098...@googlegroups.com... > > 在 2016年10月20日星期四 UTC+8下午11:04:38，Frank Millman写道： > > wrote in message > > news:01cfd810-0561-40b1-a834-95a73dad6...@googlegroups.com... > > > > Hi Frank, > > > > thanks for your kind help. What confused me is at this line: > > > > >>> r = r.setdefault('b', {}) > > > > and its previous one > > > > >>> r = r.setdefault('a', {}) > > > > When r.setdefault('a',{}) is run, I understand it will return an empty {}. > > At this time both r & t reference to {'a':{}}, right? So when "r = > > r.setdefault('a',{})" is run, r reference to {} while t keeps the same as > > {'a':{}}. > > > > then comes r.setdefault('b',{}). What hinder me is here. since r has > > changed its reference to {}, r.setdefault('b',{}) will return {} again. So > > what does this done to t? why at this time t changes to {'a':'b':{}}? > > Sorry for my silly here. Thanks > > > > I don't know if you have been following the other posts in this thread. > > There were some posts from Anssi Saari who was also confused by this, but > then yesterday he sent a post saying that he has now 'got it'. > > I don't think I can do better than quote his explanation of what is > happening - > > """ > OK, so what happens is that now t references the dictionary with {'a': {}} > and r references the empty dict inside that. > > So when we assign to r again, it's the empty dict inside t (the one accessed > by key 'a') that changes to {'b': {}} and t becomes {'a': {'b': {}}}. > """ > > That is exactly right. > > Does that help? > > Frank
Hi Frank, I have read Anssi's post already before I sent the post. To be frankly, I can't understand why he got the right answer. I'm sorry for my silly. "So when we assign to r again, it's the empty dict inside t (the one accessed by key 'a')". I do can't understand why this happens. that is the reason why I have asked for this once again and again. There must be some import point I missed but I don't what is it. -- https://mail.python.org/mailman/listinfo/python-list
