2018-10-09 Python22 if真假

假：

In [1]: if "":
   ...:     print("1")
   ...:     

In [2]: if None:
   ...:     print("2")
   ...:     

In [3]: if 0:
   ...:     print("3")
   ...:     

In [4]: if []:
   ...:     print("4")
   ...:     

In [5]: if {}:
   ...:     print("5")
   ...:     

In [6]: if ():
   ...:     print("6")
   ...:     

真：

In [8]: if not False:
   ...:     print("8")
   ...:     
8

In [9]: if 1:
   ...:     print("9")
   ...:     
9

In [10]: if -1:
   ....:     print("10")
   ....:     
10

In [11]: if "a":
   ....:     print("11")
   ....:     
11