关于append

灿君君

r=[]
r.append(3)
[3]


如果是这样
t=r.append(3)
t最后显示的是空值，这是为什么呢

小甲鱼

1. Python 3.6.2 (v3.6.2:5fd33b5, Jul  8 2017, 04:57:36) [MSC v.1900 64 bit (AMD64)] on win32
   
2. Type "copyright", "credits" or "license()" for more information.
   
3. >>> r = []
   
4. >>> r.append(3)
   
5. >>> r
   
6. [3]

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不会呀~

冬雪雪冬

append只改变列表本身，没有返回值

chakyam

新手经常犯的错误，注意一下就好了，list.append()不返回值

1. Python 3.5.3 (default, Jan 19 2017, 14:11:04)
   
2. [GCC 6.3.0 20170118] on linux
   
3. Type "help", "copyright", "credits" or "license" for more information.
   
4. >>> a=[]
   
5. >>> type(a.append('1'))
   
6. <class 'NoneType'>
   
7. >>>
   

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1. class list(object)
   
2. |  list() -> new empty list
   
3. |  list(iterable) -> new list initialized from iterable's items
   
4. |  
   
5. |  Methods defined here:
   
6. |  ....
   
7. |  append(...)
   
8. |      L.append(object) -> None -- append object to end
   
9. |  ...  
   

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