1、python2中，在列表推导中for关键字之后的赋值操作可能会影响到列表推导上下文中的同名变量：
Python 2.7.8 (default, Jun 30 2014, 16:03:49) [MSC v.1500 32 bit (Intel)] on win32
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>>> x='aaa'
>>> test = [x for x in 'ABC']
>>> x
'C'
python3：
>>> x='aaa'
>>> test = [x for x in 'ABC']
>>> x
'aaa'