python中for和if else的使用

In [8]: a = set('abcd')

In [9]: b = set('ef')

In [10]: def match(x,y):
....:     for i in x:
....:         for j in y:
....:             if i==j:
....:                 break
....:         else:
....:             return False
....:     return True
....:

In [11]: match(a,b)
Out[11]: False

In [12]: match(a,a)
Out[12]: True

In [13]: match(a,set('ab'))
Out[13]: False

In [14]: match(a,set('opqrsa'))
Out[14]: False

In [15]: match(b,b)
Out[15]: True