Python3 base SetDefault () finds the value based on the key and cannot find the key to add

Town Field Poem:
Cheng listens to the Tathagata language, the world name and benefit of Dayton. Be willing to do the Tibetan apostles, the broad show is by Sanfu mention.
I would like to do what I learned, to achieve a conscience blog. May all the Yimeimei, reproduce the wisdom of the body.
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Code

dict1={' son ': ' rat ', ' ugly ': ' Ox ', ' yin ': ' Tiger ', ' Mao ': ' Rabbit ', ' Chen ': ' Dragon ', ' have ': ' Snake ', ' noon ': ' Horse ', ' not ': ' sheep ', ' shen ': ' Monkey ', ' unitary ': ' Chicken ', ' xu ': ' Dog ', ' hai ': ' Pig '}# If you find the return print (Dict1.setdefault (' child)) #如果找不到, it will be added. Obviously the key ' child ' exists, then the value ' uncle ' is useless print (Dict1.setdefault (' son ', ' Uncle ')) print ( Dict1.setdefault (' vanity ', ' blog Park ') print (DICT1) #不存在键, not set value, default to Noneprint (Dict1.setdefault (' Loft '))

Result

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The essence of the blog, in the technical part, more in the town yard a poem. Python version 3.5, System Windows7.
Python is a good language and deserves to be studied hard. I am following the small Turtle Video tutorial to learn, recommended.
I am a novice, so if the content of the blog can be improved, or even the wrong place, please leave a comment, I will try to correct, strive to achieve a conscience blog.
Note: This article is only as a scientific research study, if I inadvertently violated your rights and interests, please be sure to timely inform, I will make corrections.

Python3 base SetDefault () finds the value based on the key and cannot find the key to add