title: How to use pip3 or pip in pyenv for virtual python I created？
body: <p>1）I use multi -versions，but I when I use pyenv to shift to other version（installed by  pyenv），I  cant install any package like numpy and tensorflow.</p>
  
  <pre><code>lzw@resplendent-star:~$ python3
  Python 3.8.1 (default, Apr 11 2020, 17:03:40) 
  [GCC 7.5.0] on linux
  Type "help", "copyright", "credits" or "license" for more information.
  &gt;&gt;&gt; import numpy
  Traceback (most recent call last):
    File "&lt;stdin&gt;", line 1, in &lt;module&gt;
  ModuleNotFoundError: No module named 'numpy'
  &gt;&gt;&gt; exit()
  lzw@resplendent-star:~$ sudo -H pip3 install numpy
  Requirement already satisfied: numpy in /usr/lib/python3/dist-packages
  </code></pre>
  
  <p>you could see，3.8.1 is what I installed by pyenv，but I cant install numpy for it.</p>
  
  <p>2）The worst thing，how could I use system default python？</p>