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python-switch-2-latest-python3

admin 11月 13, 2020 0

LinuxMint and Ubuntu installs python2.7 and python3.5 as default. But I want 2 install the latest Python3.6 and set it as the default python.

check current python versions

use follow commands:

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[email protected]:~$ python -V
Python 2.7.12
[email protected]:~$ python2 -V
Python 2.7.12
[email protected]:~$ python3 -V
Python 3.5.2
[email protected]:~$

install python3.6 into Linux

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$ sudo add-apt-repository ppa:jonathonf/python-3.6
$ sudo apt update
$ sudo apt install python3.6

check installed python3.6

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[email protected]:~$ python3.6 -V
Python 3.6.3

old python3.5 is still exist, and it is still the default python3.
to change python3.6 just installed as the default python3, we need the tool ‘’’update-alternatives’’’.

change default python3

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[email protected]:~$ update-alternatives --list python3
update-alternatives: error: no alternatives for python3

why like this? Cauz we didn’t maintained them.
do as follows:

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$ sudo update-alternatives --install /usr/bin/python3 python3 /usr/bin/python3.5 1
$ sudo update-alternatives --install /usr/bin/python3 python3 /usr/bin/python3.6 2

recheck alternatives:

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[email protected]:~$ update-alternatives --list python3
/usr/bin/python3.5
/usr/bin/python3.6

switch 2 the latest python3

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[email protected]:~$ sudo update-alternatives --config python3
有 2 个候选项可用于替换 python3 (提供 /usr/bin/python3)。
  选择       路径              优先级  状态
------------------------------------------------------------
  0            /usr/bin/python3.6   2         自动模式
  1            /usr/bin/python3.5   1         手动模式
* 2            /usr/bin/python3.6   2         手动模式
要维持当前值[*]请按<回车键>，或者键入选择的编号：

then specify the latest python3 as default by select numbers.

swith python2 2 python3

ps: do not do anything on python2, as many system tools may rely on it.
if you want 2 use python3 instead of python2, suggest you use virtualenv.
But, if you really really want 2 change python2 2 python3 on your system, do as follows

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sudo update-alternatives --install /usr/bin/python python /usr/local/lib/python2.7 1
sudo update-alternatives --install /usr/bin/python python /usr/local/lib/python3.x 2

then

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sudo update-alternatives --config python

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