Ubuntu 安装python3及多版本切换
<p>Ubuntu上python版本查看</p><div class="cnblogs_code">
<pre>$ python -<span style="color: rgba(0, 0, 0, 1)">V
Python </span><span style="color: rgba(128, 0, 128, 1)">2.7</span>.<span style="color: rgba(128, 0, 128, 1)">12</span></pre>
</div>
<p>1.安装3.7</p>
<p>添加源</p>
<div class="cnblogs_code">
<pre>sudo add-apt-repository ppa:deadsnakes/ppa</pre>
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<p>检查更新</p>
<div class="cnblogs_code">
<pre>sudo apt-<span style="color: rgba(0, 0, 255, 1)">get</span> update </pre>
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<p>安装python3.7</p>
<div class="cnblogs_code">
<pre>sudo apt-<span style="color: rgba(0, 0, 255, 1)">get</span> install python3.<span style="color: rgba(128, 0, 128, 1)">7</span></pre>
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<p>安装pip3</p>
<div class="cnblogs_code">
<pre>sudo apt install python3-pip</pre>
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<p>2.使用 update-alternatives 来为整个系统更改Python 版本</p>
<p>查看python替代版本信息</p>
<div class="cnblogs_code">
<pre>~$ update-alternatives --<span style="color: rgba(0, 0, 0, 1)">display python<br></span></pre>
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<p>但是结果为</p>
<div class="cnblogs_code">
<pre>update-alternatives: error: no alternatives <span style="color: rgba(0, 0, 255, 1)">for</span> python</pre>
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<p>python的替代版本尚未被update-alternatives</p>
<p>查看python的位置</p>
<div class="cnblogs_code">
<pre><span style="color: rgba(0, 0, 0, 1)">$ whereis python
python: </span>/usr/bin/python2.<span style="color: rgba(128, 0, 128, 1)">7</span> /usr/bin/python3.<span style="color: rgba(128, 0, 128, 1)">7</span> /usr/bin/python3.5m /usr/bin/python3.7m /usr/bin/python3.<span style="color: rgba(128, 0, 128, 1)">5</span> /usr/bin/python /usr/lib/python2.<span style="color: rgba(128, 0, 128, 1)">7</span> /usr/lib/python3.<span style="color: rgba(128, 0, 128, 1)">7</span> /usr/lib/python3.<span style="color: rgba(128, 0, 128, 1)">5</span> /etc/python2.<span style="color: rgba(128, 0, 128, 1)">7</span> /etc/python3.<span style="color: rgba(128, 0, 128, 1)">7</span> /etc/python3.<span style="color: rgba(128, 0, 128, 1)">5</span> /etc/python /usr/local/lib/python2.<span style="color: rgba(128, 0, 128, 1)">7</span> /usr/local/lib/python3.<span style="color: rgba(128, 0, 128, 1)">7</span> /usr/local/lib/python3.<span style="color: rgba(128, 0, 128, 1)">5</span> /usr/share/python /usr/share/man/man1/python.<span style="color: rgba(128, 0, 128, 1)">1</span>.gz</pre>
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<p>更新一下替代列表</p>
<div class="cnblogs_code">
<pre>$ sudo update-alternatives --install /usr/bin/python python /usr/bin/python2.<span style="color: rgba(128, 0, 128, 1)">7</span> <span style="color: rgba(128, 0, 128, 1)">1</span><span style="color: rgba(0, 0, 0, 1)">
update</span>-alternatives: <span style="color: rgba(0, 0, 255, 1)">using</span> /usr/bin/python2.<span style="color: rgba(128, 0, 128, 1)">7</span> to provide /usr/bin/python (python) <span style="color: rgba(0, 0, 255, 1)">in</span><span style="color: rgba(0, 0, 0, 1)"> auto mode
baby@ubuntu:</span>~$ sudo update-alternatives --install /usr/bin/python python /usr/bin/python3.<span style="color: rgba(128, 0, 128, 1)">7</span> <span style="color: rgba(128, 0, 128, 1)">2</span><span style="color: rgba(0, 0, 0, 1)">
update</span>-alternatives: <span style="color: rgba(0, 0, 255, 1)">using</span> /usr/bin/python3.<span style="color: rgba(128, 0, 128, 1)">7</span> to provide /usr/bin/python (python) <span style="color: rgba(0, 0, 255, 1)">in</span> auto mode</pre>
</div>
<p>查看python替代版本信息</p>
<div class="cnblogs_code">
<pre>$ update-alternatives --display python python -<span style="color: rgba(0, 0, 0, 1)"> auto mode
link best version </span><span style="color: rgba(0, 0, 255, 1)">is</span> /usr/bin/python3.<span style="color: rgba(128, 0, 128, 1)">7</span><span style="color: rgba(0, 0, 0, 1)">
link currently points to </span>/usr/bin/python3.<span style="color: rgba(128, 0, 128, 1)">7</span><span style="color: rgba(0, 0, 0, 1)">
link python </span><span style="color: rgba(0, 0, 255, 1)">is</span> /usr/bin/<span style="color: rgba(0, 0, 0, 1)">python
</span>/usr/bin/python2.<span style="color: rgba(128, 0, 128, 1)">7</span> - priority <span style="color: rgba(128, 0, 128, 1)">1</span>
/usr/bin/python3.<span style="color: rgba(128, 0, 128, 1)">7</span> - priority <span style="color: rgba(128, 0, 128, 1)">2</span></pre>
</div>
<p>查看python版本</p>
<div class="cnblogs_code">
<pre>$ python -<span style="color: rgba(0, 0, 0, 1)">V
Python </span><span style="color: rgba(128, 0, 128, 1)">3.7</span>.<span style="color: rgba(128, 0, 128, 1)">9</span></pre>
</div>
<p>3.切换版本</p>
<p>切换到2.7</p>
<div class="cnblogs_code">
<pre>$ sudo update-alternatives --<span style="color: rgba(0, 0, 0, 1)">config python
There are </span><span style="color: rgba(128, 0, 128, 1)">2</span> choices <span style="color: rgba(0, 0, 255, 1)">for</span> the alternative python (providing /usr/bin/<span style="color: rgba(0, 0, 0, 1)">python).
Selection Path Priority Status
</span>------------------------------------------------------------
* <span style="color: rgba(128, 0, 128, 1)">0</span> /usr/bin/python3.<span style="color: rgba(128, 0, 128, 1)">7</span> <span style="color: rgba(128, 0, 128, 1)">2</span><span style="color: rgba(0, 0, 0, 1)"> auto mode
</span><span style="color: rgba(128, 0, 128, 1)">1</span> /usr/bin/python2.<span style="color: rgba(128, 0, 128, 1)">7</span> <span style="color: rgba(128, 0, 128, 1)">1</span><span style="color: rgba(0, 0, 0, 1)"> manual mode
</span><span style="color: rgba(128, 0, 128, 1)">2</span> /usr/bin/python3.<span style="color: rgba(128, 0, 128, 1)">7</span> <span style="color: rgba(128, 0, 128, 1)">2</span><span style="color: rgba(0, 0, 0, 1)"> manual mode
Press </span><enter> to keep the current choice[*], or type selection number: <span style="color: rgba(128, 0, 128, 1)">1</span><span style="color: rgba(0, 0, 0, 1)">
update</span>-alternatives: <span style="color: rgba(0, 0, 255, 1)">using</span> /usr/bin/python2.<span style="color: rgba(128, 0, 128, 1)">7</span> to provide /usr/bin/python (python) <span style="color: rgba(0, 0, 255, 1)">in</span><span style="color: rgba(0, 0, 0, 1)"> manual mode
baby@ubuntu:</span>~$ python -<span style="color: rgba(0, 0, 0, 1)">V
Python </span><span style="color: rgba(128, 0, 128, 1)">2.7</span>.<span style="color: rgba(128, 0, 128, 1)">12</span></pre>
</div>
<p>pip版本</p>
<div class="cnblogs_code">
<pre>$ pip -<span style="color: rgba(0, 0, 0, 1)">V
pip </span><span style="color: rgba(128, 0, 128, 1)">8.1</span>.<span style="color: rgba(128, 0, 128, 1)">1</span> <span style="color: rgba(0, 0, 255, 1)">from</span> /usr/lib/python2.<span style="color: rgba(128, 0, 128, 1)">7</span>/dist-packages (python <span style="color: rgba(128, 0, 128, 1)">2.7</span>)</pre>
</div>
<p>切换到3.7</p>
<div class="cnblogs_code">
<pre>sudo update-alternatives --<span style="color: rgba(0, 0, 0, 1)">config python
There are </span><span style="color: rgba(128, 0, 128, 1)">2</span> choices <span style="color: rgba(0, 0, 255, 1)">for</span> the alternative python (providing /usr/bin/<span style="color: rgba(0, 0, 0, 1)">python).
Selection Path Priority Status
</span>------------------------------------------------------------
<span style="color: rgba(128, 0, 128, 1)">0</span> /usr/bin/python3.<span style="color: rgba(128, 0, 128, 1)">7</span> <span style="color: rgba(128, 0, 128, 1)">2</span><span style="color: rgba(0, 0, 0, 1)"> auto mode
</span>* <span style="color: rgba(128, 0, 128, 1)">1</span> /usr/bin/python2.<span style="color: rgba(128, 0, 128, 1)">7</span> <span style="color: rgba(128, 0, 128, 1)">1</span><span style="color: rgba(0, 0, 0, 1)"> manual mode
</span><span style="color: rgba(128, 0, 128, 1)">2</span> /usr/bin/python3.<span style="color: rgba(128, 0, 128, 1)">7</span> <span style="color: rgba(128, 0, 128, 1)">2</span><span style="color: rgba(0, 0, 0, 1)"> manual mode
Press </span><enter> to keep the current choice[*], or type selection number: <span style="color: rgba(128, 0, 128, 1)">2</span><span style="color: rgba(0, 0, 0, 1)">
update</span>-alternatives: <span style="color: rgba(0, 0, 255, 1)">using</span> /usr/bin/python3.<span style="color: rgba(128, 0, 128, 1)">7</span> to provide /usr/bin/python (python) <span style="color: rgba(0, 0, 255, 1)">in</span><span style="color: rgba(0, 0, 0, 1)"> manual mode
baby@ubuntu:</span>~$ python -<span style="color: rgba(0, 0, 0, 1)">V
Python </span><span style="color: rgba(128, 0, 128, 1)">3.7</span>.<span style="color: rgba(128, 0, 128, 1)">9</span></pre>
</div>
<p>安装pip</p>
<div class="cnblogs_code">
<pre>sudo apt install python3-pip</pre>
</div>
<p>pip版本</p>
<div class="cnblogs_code">
<pre> pip -<span style="color: rgba(0, 0, 0, 1)">V
pip </span><span style="color: rgba(128, 0, 128, 1)">8.1</span>.<span style="color: rgba(128, 0, 128, 1)">1</span> <span style="color: rgba(0, 0, 255, 1)">from</span> /usr/lib/python3/dist-packages (python <span style="color: rgba(128, 0, 128, 1)">3.7</span>)</pre>
</div>
<p>pip的版本随着python版本切换</p><br><br>
来源：https://www.cnblogs.com/baby123/p/14234171.html
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