从集合中选择单个项目:Python

一个更简单的解决方案是使用元组解包.这已经做了你想要的一切,包括检查它只包含一个项目.

单项:

 >>> name, = (name for name in ('bob','fred') if name=='bob')
 >>> name
 'bob'

过多的物品:

>>> name, = (name for name in ('bob','bob') if name=='bob')
Traceback (most recent call last):
  File "", line 1, in 
ValueError: too many values to unpack

没有相关产品:

>>> name, = (name for name in ('fred','joe') if name=='bob')
Traceback (most recent call last):
  File "", line 1, in 
ValueError: need more than 0 values to unpack