title: Install PIP3 and PYTHON3.7 on Docker Ubuntu 18.04
body: <p>I have to install <code>Python3.7</code> and <code>pip3</code> for Python3.7 on my Docker Ubuntu18.04. I can install the <code>3.7</code>, but I cannot get rid of <code>pip3</code> for <code>Python3.6</code>:</p>
  
  <pre><code>FROM ubuntu:18.04
  # ...
  RUN apt-get update &amp;&amp; apt-get install -y \
          software-properties-common
      RUN add-apt-repository ppa:deadsnakes/ppa
      RUN apt-get update &amp;&amp; apt-get install -y \
          python3.7 \
          python3-pip
      RUN python3.7 -m pip install pip
      RUN apt-get update &amp;&amp; apt-get install -y \
          python3-distutils \
          python3-setuptools
  </code></pre>
  
  <p>and I have</p>
  
  <pre><code>root@ef0c924ba7fa:/tornado_api# python3.7 --version
  Python 3.7.3
  root@ef0c924ba7fa:/tornado_api# pip3 --version
  pip 9.0.1 from /usr/lib/python3/dist-packages (python 3.6)
  </code></pre>
  
  <p>while it should be <code>pip3</code> under <code>/usr/lib/python3.7/</code></p>
  
  <p>Currently, I get</p>
  
  <pre><code>root@ef0c924ba7fa:/tornado_api# which pip3
  /usr/bin/pip3
  root@ef0c924ba7fa:/tornado_api# readlink $(which pip3)
  root@ef0c924ba7fa:/tornado_api# 
  </code></pre>