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

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

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

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

class list(object)
 |  list() -> new empty list
 |  list(iterable) -> new list initialized from iterable's items
 |  
 |  Methods defined here:
 |  ....
 |  append(...)
 |      L.append(object) -> None -- append object to end
 |  ...