title: zlib1g-dev is already installed but shows ModuleNotFoundError: No module named 'zlib'
body: <p>In my Debian 10 OS, I have several Python versions as 2.7, 3.7 and 3.8. For Python 3.8, pip did not work(no module name pip) and I tried to install pip for Python 3.8 with 'sudo python3.8 get-pip.py' and it showed below error.</p>
  <pre><code>Traceback (most recent call last):
    File &quot;&lt;frozen zipimport&gt;&quot;, line 520, in _get_decompress_func
  ModuleNotFoundError: No module named 'zlib'
  
  During handling of the above exception, another exception occurred:
  
  Traceback (most recent call last):
    File &quot;&lt;frozen zipimport&gt;&quot;, line 568, in _get_data
    File &quot;&lt;frozen zipimport&gt;&quot;, line 523, in _get_decompress_func
  zipimport.ZipImportError: can't decompress data; zlib not available
  
  During handling of the above exception, another exception occurred:
  
  Traceback (most recent call last):
    File &quot;get-pip.py&quot;, line 23704, in &lt;module&gt;
      main()
    File &quot;get-pip.py&quot;, line 198, in main
      bootstrap(tmpdir=tmpdir)
    File &quot;get-pip.py&quot;, line 82, in bootstrap
      from pip._internal.cli.main import main as pip_entry_point
    File &quot;&lt;frozen zipimport&gt;&quot;, line 241, in load_module
    File &quot;&lt;frozen zipimport&gt;&quot;, line 709, in _get_module_code
    File &quot;&lt;frozen zipimport&gt;&quot;, line 570, in _get_data
  zipimport.ZipImportError: can't decompress data; zlib not available
  </code></pre>
  <p>Then, I tried to install zlib with 'sudo apt install zlib1g-dev' but it showed that package is already in the system.</p>
  <pre><code>Reading package lists... Done
  Building dependency tree       
  Reading state information... Done
  zlib1g-dev is already the newest version (1:1.2.11.dfsg-1).
  The following packages were automatically installed and are no longer required:
    adb android-libadb android-libbase android-libboringssl
    android-libcrypto-utils android-libcutils android-liblog
    android-sdk-platform-tools-common arch-test bridge-utils cloud-image-utils
    debootstrap distro-info genisoimage libayatana-appindicator3-1
    libayatana-ido3-0.4-0 libayatana-indicator3-7 libboost-log1.67.0
    libboost-program-options1.67.0 libboost-regex1.67.0
    libboost-serialization1.67.0 liblxc1 libmotif-common libnma0 libpam-cgfs
    libprotobuf-lite17 libsdl2-image-2.0-0 libu2f-udev libxm4 lxc lxc-templates
    lxcfs network-manager-gnome qemu-utils squashfs-tools uidmap
  Use 'sudo apt autoremove' to remove them.
  0 upgraded, 0 newly installed, 0 to remove and 127 not upgraded.
  </code></pre>