python类中属性逗号引发的类型改变

不注意点了个逗号引发了类型改变

[shangbl@newsvn ~]$ cat test.py 
class AB1:
   a="a"

class AB12:
   a="a",

print(type(AB1.a))
print(type(AB12.a))
[shangbl@newsvn ~]$ python test.py 
<type 'str'>
<type 'tuple'>
[shangbl@newsvn ~]$ cat test.