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I used pip3 to install virtualenv but I can't create venv and also I can't uninstall virtualenv

I'm using Linux Mint 20.2 with two directories / and /home.
I used the following command to install virtualenv:
>>> sudo pip3 install virtualenv
It worked fine and it installed in the following path:
>>> virtualenv --version
virtualenv 20.0.17 from /usr/lib/python3/dist-packages/virtualenv/__init__.py
But when I tried to create an environment I got the following error:
>>> python3 -m venv article
The virtual environment was not created successfully because ensurepip is not
available. On Debian/Ubuntu systems, you need to install the python3-venv
package using the following command.
apt install python3.8-venv
You may need to use sudo with that command. After installing the python3-venv
package, recreate your virtual environment.
Failing command: ['/home/username/article_tools/article/bin/python3', '-Im', 'ensurepip', '--upgrade', '--default-pip']
When I tried to uninstall it to install it using [b]sudo apt install python3.8-venv[/b], I got the following error:
>>> sudo pip3 uninstall virtualenv
Found existing installation: virtualenv 20.0.17
Not uninstalling virtualenv at /usr/lib/python3/dist-packages, outside environment /usr
Can't uninstall 'virtualenv'. No files were found to uninstall.
How can I fix it? By fix, I mean installing virtualenv in a way that I don't get such errors.

The fundamental problem here seems to be that you are mixing up two different packages.
Python 3 comes with a built-in virtual environment module venv which is however not installed by default on Debian-based platforms. Like the error message says, apt-get install -y python3-venv will install this package, which you can then use with python3 -m venv.
virtualenv is a separate third-party package which you invoke with the command virtualenv. It's not a bad alternative, but if you are only just learning, I would suggest you simply ignore it for the time being.

Installing pip and numpy on Unix server without root access

I know this question has been asked and answered a number of times but none of those solutions have worked for me. I have installed Python 2.7 into a local directory and added it to my path. When I try to install numpy i get the following error:
ImportError: No module named setuptools
I cannot simply sudo apt-get install python-setuptools because i don't have root access.
I need to install numpy and ideally have pip working for future applications.

0) Try to install packages that are isolated to the current user, use the --user flag:
pip install --user SomeProject
1a) I agree with #Pi Marillion here, use an isolated conda environment if you don't have root access. This way you keep your path clean.
To install conda:
Since I don't know about your OS, go to https://docs.conda.io/en/latest/miniconda.html
After installation, update your conda (just in case):
conda update conda
To list the installed packages, you can do
conda list
You should see python installed. you can start an interpreter by typing python in the terminal.
There's conda cheat sheet that I found incredibly helpful:
https://docs.conda.io/projects/conda/en/latest/user-guide/cheatsheet.html
b) Now try installing via pip and I think you might need python 3.x for setuptools.
https://packaging.python.org/tutorials/installing-packages/#id13
2) If this does not work you can still try
https://packaging.python.org/guides/installing-stand-alone-command-line-tools/
Hope this helps :)

First try easy_install --user setuptools pip. If that doesn't work you need to install things manually.
Download setuptools-*.zip from https://pypi.org/project/setuptools/#files. Unzip the archive, cd into the new directory and run python2.7 setup.py install.
Then try pip install. If it still doesn't work reinstall pip: download get-pip.py and run python get-pip.py --user.

Python on anaconda cannot find azure.mgmt.datafactory

I am trying to run this tutorial
https://learn.microsoft.com/en-US/azure/data-factory/quickstart-create-data-factory-python
but I fail to install the packages. I tried several installations but I keep getting the error No module named 'azure.mgmt.datafactory' when trying to run from azure.mgmt.datafactory import DataFactoryManagementClient.
I am using anaconda and windows 10.
I tried running the recommended anaconda packages https://anaconda.org/anaconda/azure and https://anaconda.org/clinicalgraphics/azure-mgmt-resource under a python 3.5 environment and I also tried to manually install everything from github (https://github.com/Azure/azure-sdk-for-python) using
git clone git://github.com/Azure/azure-sdk-for-python.git
cd azure-sdk-for-python
python setup.py install
In both the normal (Python 3.6) and the new (Python 3.5, using Anaconda version with Python 3.5) environment. None of this worked.
What am I missing?
(Note that from azure.mgmt.resource import ResourceManagementClient worked fine with the anaconda installation)
EDIT
After the first response, I ran the following commands from the powershell
pip install azure-mgmt-resource
pip install azure-mgmt-datafactory
pip install azure-mgmt
which resulted in ModuleNotFoundError: No module named 'azure.mgmt'
Uninstalling the three packages and installing azure-mgmt as a first one did not solve the issue either. However, I don't know how to uninstall the manually installed package from python setup.py install, which still might be an issue.

Have you tried pip install in powershell/cmd?
pip install azure-mgmt-datafactory
Update (Jan's answer):
pip freeze > requirements.txt
pip uninstall -r requirements.txt
python -m pip install azure-common
python -m pip install azure-mgmt
python -m pip install azure-mgmt-datafactory (this might not be needed as it comes with azure-mgmt)

Ok, this is how I got the required azure libraries to work (thx to Saul Cruy, who gave me the idea)
Using this post What is the easiest way to remove all packages installed by pip?, I created a requirements file in PowerShell
pip freeze > requirements.txt
In this file, I manually kept only the entries with azure.
Then, I deleted all packages in the file
pip uninstall -r requirements.txt
The steps above were repeated twice, as upon first delete, some azure packages survived.
Then, I ran (all in PowerShell, in that order)
python -m pip install azure-common
python -m pip install azure-mgmt
python -m pip install azure-mgmt-datafactory
The reason might(!) be that installing packages in the anaconda console using the conda commands causes confusion in the dependencies (I tried a similar approach in a conda environment as it seemed like a good idea to seperate the azure packages from the other ones, but without success).

Error With Installing Virtualenv With Pip and Homebrew

I am trying to get a nice clean Python environment setup on OSX 10.9. I've installed Python with Homebrew and set my PATH variables so...
> which python
/usr/local/bin/python
and
> which pip
/usr/local/bin/pip
so when I look at my /usr/local/bin :
pip -> ../Cellar/python/2.7.6/bin/pip
python -> ../Cellar/python/2.7.6/bin/python
then when I run:
> pip install virtualenv
I get permission errors on /usr/local/bin/virtualenv:
...
running install_scripts
Installing virtualenv script to /usr/local/bin
error: /usr/local/bin/virtualenv: Permission denied
I thought that by using Homebrew I could use pip and avoid using sudo to install virtualenv. Am I doing something wrong here?

Ok! I managed to fix this myself.
I deleted all the virtualenv related things from /usr/local/bin (they had been installed under root for some reason and this was causing my permission issues.).
Then I did a pip uninstall virtualenv to get rid of other instances of virtualenv, as there was still one in /usr/local/lib/python2.7/site-packages/
Then a simple pip install virtualenv and things work fine now!

Most likely HomeBrew does some magic so that running brew install allows writing to /usr/local/bin, but this privilege is not available to normal commands. This is a guess, I didn't investigate this further.
Install virtualenv with brew:
brew install pyenv-virtualenv

This command:
pip install virtualenv
runs pip from your first directory from $PATH environment variable, which is usually system wide, thus when you run in this way - you are trying to install it globall.
You should install you your environment in your $HOME directory:
virtualenv $HOME/myvirpython
and later:
$HOME/myvirpython/bin pip install something
Additionally you should read this:
https://docs.brew.sh/Homebrew-and-Python

pip freeze does not show all installed packages

I am using a virtualenv. I have fabric installed, with pip. But a pip freeze does not give any hint about that. The package is there, in my virtualenv, but pip is silent about it. Why could that be? Any way to debug this?

I just tried this myself:
create a virtualenv in to the "env" directory:
$virtualenv2.7 --distribute env
New python executable in env/bin/python
Installing distribute....done.
Installing pip................done.
next, activate the virtual environment:
$source env/bin/activate
the prompt changed. now install fabric:
(env)$pip install fabric
Downloading/unpacking fabric
Downloading Fabric-1.6.1.tar.gz (216Kb): 216Kb downloaded
Running setup.py egg_info for package fabric
...
Successfully installed fabric paramiko pycrypto
Cleaning up...
And pip freeze shows the correct result:
(env)$pip freeze
Fabric==1.6.1
distribute==0.6.27
paramiko==1.10.1
pycrypto==2.6
wsgiref==0.1.2
Maybe you forgot to activate the virtual environment? On a *nix console type which pip to find out.

You can try using the --all flag, like this:
pip freeze --all > requirements.txt

Although your problem was specifically due to a typo, to help other users:
pip freeze doesn't show the dependencies that pip depends on. If you want to obtain all packages you can use pip freeze --all or pip list.

If you have redirected all the pre-installed packages in a file named pip-requirements.txt then it is pretty simple to fix the above issue.
1) Delete your virtualenv folder or create new one (I am giving it a name as venv)
rm -rf venv && virtualenv venv
2) Install all the requirements/dependencies from the pip-requirements.txt
pip install -r pip-requirements.txt
3) Now you can check the installed packages for your Django application
pip freeze
4) If you had forgotten to update your requirements file(pip-requirements.txt), then install fabric again (Optional Step)
Note: After installing any dependency for your Django app, always update the requirements in any file as follows (make sure your virtualenv is activated)
pip freeze > pip requirements.txt
That's it.

Adding my fix in addition of above fix also ,
I was also facing the same issue on windows,even after activating the virtualenv too pip freeze was not giving me all list of installed packages. So i upgraded my pip with python -m pip install --upgrade pip command and then used pip freeze.
This time it worked and gave me all list of installed packages.

This might be stupid but I have got the same problem. I solved it by refreshing vs code file directory (inside vscode there is a reload button). :)

If none of the above answers are working for you.
As with me you might have problem in you venv and pip configuration.
Go inside your venv/bin and open pip and see the 2nd line as:
'''exec' "path/to/yourvenv/bin/python3" "$0" "$#"
See if this line is correctly pointing inside your venv or not
For example in my case.
I initially named my virtual environment as venv1
and later just renamed it to venv2.
In doing so my pip file 2nd line had: '''exec' "venv1/bin/python3" "$0" "$#"
which to work properly should have: '''exec' "venv2/bin/python3" "$0" "$#" notice "venv2" not "venv1" since venv1 in now renamed to venv2.
Due to this python was looking inside pip of venv2 and throwing error or not working as desired.

For those who added Python modules via PyCharm IDE, after generating a virtual environment from the command prompt, good luck! You will need to rebuild the requirements.txt file manually with the ones missing by first running pip3 freeze and adding what is missing from PyCharm.
I highly suggest switching to Visual Studio Code.