ubuntu16.04中預設已經安裝了python2.7和python3.5

[email protected]:/usr/bin$ ls |grep python
dh_python2
dh_python3
python
python2
python2.7
python2.7-config
python2-config
python3
python3.5
python3.5m
python3m
python-config
x86_64-linux-gnu-python2.7-config
x86_64-linux-gnu-python-config

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怎麼切換？

1.現在是2.7

hanli@ubuntu:/usr/bin$ python
Python 2.7.12 (default, Nov 19 2016, 06:48:10) 

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2.執行兩條命令

hanli@ubuntu:/usr/bin$ sudo update-alternatives --install /usr/bin/python python /usr/bin/python2 100
update-alternatives: using /usr/bin/python2 to provide /usr/bin/python (python) in auto mode
hanli@ubuntu:/usr/bin
 
$ sudo update-alternatives --install /usr/bin/python python /usr/bin/python3 150
update-alternatives: using /usr/bin/python3 to provide /usr/bin/python (python) in auto mode

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3.再次檢視已經變成3.5了

hanli@ubuntu:/usr/bin$ python
Python 3.5.2 (default, Nov 17 2016, 17:05:23) 

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4.怎麼隨意切換

[email protected]:/usr/bin$ sudo update-alternatives --config python
There are 2 choices for the alternative python (providing /usr/bin/python).

  Selection    Path              Priority   Status
------------------------------------------------------------
 

* 0            /usr/bin/python3   150       auto mode
  1            /usr/bin/python2   100       manual mode
  2            /usr/bin/python3   150       manual mode

Press <enter> to keep the current choice[*], or type selection number: 1
update-alternatives: using /usr/bin/python2 to provide /usr/bin/python (python) in manual mode

#數字前面有*號表示是當前使用版本，輸入1切換到2.7，再次檢視如下

[email protected]:/usr/bin$ sudo update-alternatives --config python
There are 2 choices for the alternative python (providing /usr/bin/python).

  Selection    Path              Priority   Status
------------------------------------------------------------
  0            /usr/bin/python3   150       auto mode
* 1            /usr/bin/python2   100       manual mode
  2            /usr/bin/python3   150       manual mode

Press <enter> to keep the current choice[*], or type selection number: