在我的centos 6.8 里，既有python2，也有python3，
但是出现如下情况：
>>> list({1:'a','dd':2})
[1, 'dd']
>>> ^[[A^[[A^[[B^[[B
File "<stdin>", line 1
^
SyntaxError: invalid syntax
>>> ^[[A
File "<stdin>", line 1
^
SyntaxError: invalid syntax
>>> exit()
[oh@localhost git]$ python
Python 2.6.6 (r266:84292, Aug 18 2016, 14:53:48)
[GCC 4.4.7 20120313 (Red Hat 4.4.7-17)] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> list()
[]
>>> list()
[]
>>>
----------------------------------------------
也就是说python3里，没有记住命令，当按了向上键时！！！
而python2里却有？？？why
---------------