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Can't fix "zipimport.ZipImportError: can't decompress data; zlib not available" when I type in "python3.6 get-pip.py"

I was trying to install Django. Turns out that course's teacher said that we will be working with Python 3.6
I install Python 3.6. Now it's my default, it somewhat replaced the last version I had; which is Python 3.5.
Everything ok until that. But when I want to install Django doing
"pip3 install django", it tells me that the module is already satisfied and therefore installed.
I run "python3" command into my terminal. It runs Python 3.6. I try to import Django, and boom... "No module named 'django'".
Then I realized pip3 was actually installing my modules into Python 3.5 and not 3.6. So what I do is to install pip in Python 3.6.
I download get-pip.py and proceed to execute it with Python 3.6 typing in "python3.6 get-pip.py".
Here is when the damn "zipimport.ZipImportError: can't decompress data; zlib not available" goes in. I've tried a ton of things and no one of them fixed the %^$! problem. I'm really tired.
What I have already tried:
python3.6 -m pip install django, which output is "/usr/local/bin/python3.6: No module named pip"
apt install zlib, which output is "E: Unable to locate package zlib"
apt install zlib1g-dev, which says that it's already installed; the problem persists though.

I also came across this problem (while creating a simple installer for pyenv). Here's how I solved it for Mac and Linux:
Ubuntu 20.04, 18.04
You need the zlib development files, and probably zlib itself too:
sudo apt install -y zlib1g-dev zlibc
If you're missing zlib, it's likely that the next problem you'll run into is with openssl, so it's probably best to get that now as well:
sudo apt install -y libssl-dev
sudo apt install -y libssl1.1 || sudo apt install -y libssl1.0
macOS
I believe this comes with XCode CLI Tools (or at least I didn't have to custom install it Big Sur):
xcode-select --install

For me it worked in RHEL:
$ yum install zlib-devel

Suggested solutions (installing zlib1g-dev or zlib-devel) seem to resolve the issue in most cases. Here is one edge case I've encountered recently: whatever you are trying to run might use zlib via symlink which might be broken.
In my case I was trying to run a build of a 3rd-party software which already had python and all necessary libs being emebedded into it. It was packaged as a tar.gz archive. Unpacking the archive on a Windows machine and then copying the contents to another linux machine destroyed all the symlinks (if you do ls -l in a folder with symlinks you would see that all of them have size 0 and do not point to anything). Copying tar.gz to the linux machine directly and unpacking it there resolved the issue.
P.S. I know it's an edge case scenario but it took me and one more developer quite a while to figure it out so I think it's worth mentioning here, just in case someone gets as unlucky as I got.

Its solves my issue for centos 7.6 :-
yum install zlib-deve

How do I replace a Python installed from source with a packaged version?

As Python 3.7 was being prepared I installed Python 3.7.0b3 from source. Now 3.7 is out and I want to use the version packaged for Ubuntu. So I've done
apt-get install python3.7
but
$ which python3.7
/usr/local/bin/python3.7
$ /usr/local/bin/python3.7 --version
Python 3.7.0b3
How does one uninstall a Python installed from source (on Ubuntu)?
Or how can I replace it with the apt repo packaged version?

Since you opened a bounty, I can't vote to close as a duplicate, but this question would seem to provide a possible solution. Quoting from the accepted answer:
You can use checkinstall to remove Python. The idea is:
Install checkinstall
Use
checkinstall to make a deb of your
Python installation
Use dpkg -r to
remove the deb.
checkinstall basically wraps a make install command and creates a Debian .deb package based on what was installed. Then, you can just uninstall that package to reverse make install completely. To be perfectly safe you may want to uninstall the packaged Python 3.7 first and reinstall it afterwards to avoid any conflicts (I wouldn't expect any, though, since the packaged version lives in /usr while your source version lives in /usr/local).
If you don't have your source files around anymore, you can always download them again (https://www.python.org/downloads/release/python-370b3/) and rebuild Python. Specifically, the checkinstall commands would look something like this:
sudo apt install checkinstall
wget https://www.python.org/ftp/python/3.7.0/Python-3.7.0b3.tgz
tar xf Python-3.7.0b3.tgz
cd Python-3.7.0b3
./configure && make
sudo checkinstall -D --fstrans=no make install
sudo dpkg -r Python-3.7.0b3.deb
(-D creates a Debian package, --fstrans=no disables use of a temporary directory for installation).

Since I was also moving to python 3.7, I came across this question and decided to answer it, as well as finish my installation.
This are the two sources, which I used for installing python 3.7 on ubuntu 16.04:
https://askubuntu.com/questions/865554/how-do-i-install-python-3-6-using-apt-get
https://superuser.com/questions/241865/updating-python-on-ubuntu-system
Apparently from the first source the deadsnakes PPA contain Python 3.7 - Link: https://github.com/deadsnakes/python3.7/tree/ubuntu/xenial/Python
So following from my first source, I used the following commands to install Python 3.7:
sudo add-apt-repository ppa:deadsnakes/ppa
sudo apt-get update
sudo apt-get install python3.7
It installed Python 3.7 successfully but my Python 3.5.2 remains default. You can invoke/use Python 3.7 by running the commands:
python3.7 script.py
It works, so I decided to set Python 3.7 as default by removing python 3.5, but I came across my second source, and just decided to stick with using python3.7, when running my script in the terminal.
Apparently it says:
Ubuntu policies extensively for writing end-user software. So basically, a large part of the system is written in Python. To switch to Python 3.7, there needs to be done a piece of work consisting of updating and re-testing all the scripts.
So to say you can't just switch to Python 3.7 and delete the older version.
Also from a comment from my first source it states deleting the older version might break the system. I haven't been around to deleting my older version in case it might break the system, but since you are asking for how to download Python 3.7, I think my first source and the first part of my answer should to the work.
I hope it helps :)

It seems that your Python built from source is under /usr/local, and your PATH variable has /usr/local/bin before /usr/bin, since running python3.7 gets you the one under /usr/local rather than the packaged one which would be /usr/bin/python3.7.
Look at your PATH to verify this.
echo $PATH
(When you run a program in bash, that particular running bash instance will remember the location and not rescan the directories in the PATH for that program again, so it will not notice a new file that has appeared somewhere earlier in the PATH. You can prevent this by running hash -r to reset the cache or by just exiting the shell and launching it again.)
I presume your goal is for python3.7 (or any of the other commands provided by Python) to run the versions from your packaged install in /usr.
Unfortunately the python build process does not provide an uninstall method -- the only automated way to remove just the files installed by a source Python install requires using other tools ahead of time (such as checkinstall).
So you have some choices :
Change your PATH so that /usr/local/bin is after /usr/bin. To do this, edit your ~/.profile file or whatever other script you have configuring your PATH and logout/login. This will also affect any other commands you run that are available in both /usr/local/bin and /usr/bin.
Remove /usr/local and reinstall anything else you want there. If a Python install is the only thing in your /usr/local, or if you can easily reinstall anything else you had there, this might be the way to go.
Painstakingly figure out what files under /usr/local/bin were part of Python and remove them. You might be able use the corresponding files in /usr/bin from your installed python3 packages as a starting point to figure out the similar names for /usr/local/bin.
One-liner to get the list of files in /usr/bin from installed python3* packages:
$ for pkg in $(dpkg -l 'python3*' | grep '^ii' | cut -f 3 -d' '); do dpkg -L $pkg | grep '^/usr/bin/'; done | sort
This should produce a list of files like:
/usr/bin/2to3-3.x
/usr/bin/chardet3
...
(I've tested this one-liner on Debian, I'm not sure if any changes are required for Ubuntu)

Python not finding pip modules MacOS

I have installed some modules using pip and whenever I try to import them in Python I am told that no module exists. I think there is something wrong with my paths. This is some terminal output, does anyone know how I can fix this?
Nicks-MacBook-Pro:~ nickporter$ which python
/usr/bin/python
Nicks-MacBook-Pro:~ nickporter$ which pip
/usr/local/bin/pip
Nicks-MacBook-Pro:~ nickporter$

You can use pip freeze to find the packages installed.
I do not know whether you use a virtualenv. If you use it, you have to source it, to activate it.

It looks like you probably have multiple installations of Python or pip (or both). First, determine if you have multiple Python binaries installed and decide on the one you want to use by default.
You clearly have /usr/bin/python...check if there is another one in /usr/local/bin/python. If you do have one in /usr/local/bin, I'm guessing you installed it with Homebrew. Pick the Python you want to use (if there are multiple) by playing with your PATH. If you want to use /usr/local/bin/python (assuming it exists) ensure /usr/local/bin comes before /usr/bin in your PATH.
Once you do that, I would remove your current pip. After you remove it, look for it again with which pip, just to make sure you don't have any old one laying around. Once you've totally removed it, reinstall.
If you're installing with Homebrew, I'd stick to using the Homebrew python and pip. If you're not using Homebrew I'd install pip using: https://bootstrap.pypa.io/get-pip.py
curl -q https://bootstrap.pypa.io/get-pip.py | sudo python

You have homebrew version of python shadowed by the system python, but because system python doesn't have pip, a pip you see is actually a brew one.
I found, that the reason for this is that brew by default names python2.7 as python2 in /usr/local/bin (probably for preventing possible compatibility issues with some system services (?)) , i.e. you may try to run python2 or try to ln /usr/local/bin/python2 /usr/local/bin/python and restart the term session.
Make sure that /usr/local/bin goes before /usr/bin and /bin in your $PATH.
BTW. brew info {package} often contains recommendations for proper configuration of packages.

Upgraded Python; Do I have to reinstall all site-packages manually?

I have upraded my Linux distro recently. Python 3.5 was replaced by Python 3.6.
All site packages I have installed with pip3 are still in the /usr/lib/python3.5/site-packages directory and Python does not find them there now, because it looks in .../python3.6/site-packages obviously.
I see the directory contents and I could manually install them again, but that does not look to me like the right way to do it. I could move the contents to the new directory, but again, this seems to me incorrect either.
How am I supposed to handle it properly?
Should I have prepared a pip3 freeze list before the upgrade?
I tried to search, but the keywords are probably too general and got many unrelated answers.

Python 3.5 was replaced by Python 3.6. But you still have the backup option of using python 3.5.
If you want to use python 3.6 you will have to reinstall all pip packages again for python 3.6. And it makes sense.
Say you were changing from 2.7 to 3.5. You would want to preserve both the environments separately. Hence 3.6 environment is different from 3.5.
A quick way to do this would be to pip freeze for 3.5 and then install those dependencies for 3.6.
pip freeze > reqs.txt
upgrade
pip install -r reqs.txt
Since you don't have this option anymore, first try and list all packages in your python3.5
for that you can install pip3.5 as answered by #kabanus.
sudo apt-get install python3=3.5.1*
sudo python3.5 easy_install.py pip
Also it's advised to use virtual environment per project so you can maintain separate environments for each of them.

I just hit the same problem upgrading from Python 3.6 to Python 3.7, I forgot to run pip freeze before I upgraded to Python 3.7. The solution that worked is to specify the --path option as the old site-packages/ directory (which was not deleted):
pip3 freeze --path /usr/local/lib/python3.6/site-packages/ > python3.6_requirements.txt
pip3 install -r python3.6_requirements.txt

This would have made things simpler for you to reinstall. Checkout the description. Using freeze you could have done something like:
$ env1/bin/pip3 freeze > requirements.txt
$ env2/bin/pip3 install -r requirements.txt
Generally the recommended method is you use a virtualenv for site packages, so you don't litter your installation areas, but TBH it never broke something for me. Another option is to check if the linux distribution has the package available for proper retrieval, as in:
sudo apt-get install python3-<somemodule>
This is what I prefer - and could have been upgraded with the distro. As for what to do now, If you really don't want to re-install everything properly you could try to cp /usr/lib/python3.5/site-packages/* /usr/lib/python3.6/site-packages. The differences between versions are not so great such that I believe most packages would work off the bat. You may have to sed to replace python3.5 with python3.6 in all files there though. Forgot delete all pyc files if you do this.
Python modules are self contained enough that if something is broken it can be handled per package, and the site packages are self contained completely, so you could always just remove everything and re-install.
A final note - you can try and install pyton3.5/pip3.5 for your linux, and then do the freeze thing. If there is no package you could install manually (whl or such) or compile a stand alone and configure the site path properly. If you want to keep things on a global site package directory or migrate to virtualenv this may be the safest option.

Ubuntu:What is the right way to reinstall from source after package was installed via apt?

I have a python package previously installed via apt(by default).
Now I want to install new version and compile it manually from the sources with all the required modules.
How can I do that?
I suppose that
apt-get purge python
And then install from sources is not possible because python have lots of dependencies and will uninstall all of them in this case.
What is the right way to do that?

Don't replace your system's default Python interpreter. It can break things which will be difficult to fix later. Instead you probably want to use virtualenv. You can then isolate any issues from your environment and have the added advantage of multiple Python installations which can tested independently.
Here is some worthwhile reading to get you started:
http://www.lorenzogil.com/blog/2010/10/29/python-deployment-tips/
http://mitchfournier.com/2010/06/25/getting-started-with-virtualenv-isolated-python-environments/
http://www.clemesha.org/blog/modern-python-hacker-tools-virtualenv-fabric-pip

sudo apt-get remove name-of-package
then
sudo apt-get autoclean
will remove the package and any dependencies that are no longer needed.