if a != None:
>>> x
=
1
>>>
not
x
False
>>> x
=
[
1
]
>>>
not
x
False
>>> x
=
0
>>>
not
x
True
>>> x
=
[
0
]
# You don't want to fall in this one.
>>>
not
x
False
在python中 None, False, 空字符串"", 0, 空列表[], 空字典{}, 空元组()都相当于False ,即:
not None == not False == not '' == not 0 == not [] == not {} == not ()
not None == not False == not '' == not 0 == not [] == not {} == not ()
![](https://img2018.cnblogs.com/blog/1413304/201906/1413304-20190627085833953-543741663.png)
if a != None:
其意思是a!=none,则执行:后面的语句