If you uninstall from the control panel, it should remove all packages with it. To ensure that your path doesn't contain your old python when you try and use anaconda, you should remove Python from your path. In windows 10:

1. From desktop go bottom left and find the menu.
2. Click system, then Advanced System Settings
3. In this window, go to the Advanced tab and click on the environment variables button.
4. From there you can edit your Path, with the edit button.
5. Make sure there is no reference to Python here. Also, all variables are separated by a ; so make sure all syntax is good before saving.
6. Install anaconda and at the end of the install it should ask if you want to make it the default Python. Say yes and every time you or another program asks for Python, it will get pointed to anaconda.

Here's the steps (my non-computer-savvy girlfriend had to figure this one out for me, but unlike all the far more complicated processes one can find online, this one works)

1. Open Control Panel
2. Click "Uninstall a Program"
3. Scroll down to Python and click uninstall for each version you don't want anymore.

This works on Windows 7 out of the box, no additional programs or scripts required.

I've found this snippet as an alternative solution. It's a more graceful removal of libraries than remaking the virtualenv:

pip freeze | xargs pip uninstall -y

In case you have packages installed via VCS, you need to exclude those lines and remove the packages manually (elevated from the comments below):

pip freeze --exclude-editable | xargs pip uninstall -y

If you have packages installed directly from github/gitlab, those will have @. Like:

django @ git+https://github.com/django.git@<sha>

You can add cut -d "@" -f1 to get just the package name that is required to uninstall it.

pip freeze | cut -d "@" -f1 | xargs pip uninstall -y

If you just want to remove all the packages you've installed (as opposed to all of Python), you'd want to nuke your site-packages directory.

To find it, from Python run >>> import some_package (where some_package is a package you've installed; setuptools is one you're likely to have), then run some_package.__file__. The output should be something like /path/to/site-packages/distribute-0.6.19-py2.6.egg/setuptools/__init__.pyc. Delete (or, better yet, rename) and recreate /path/to/site-packages. That will get rid of everything you've installed.

Please don't.

Ubuntu relies heavily on different Python versions for functionality. New releases of Ubuntu are slowly shifting to Python3, but older versions of Python are still in use.

You can list some important Ubuntu and Gnome packages on your system that depend on Python3, for example, like so:

apt-cache rdepends -i --installed --recurse python3 | \
grep -v " " | sort -u | grep -E "ubuntu|gnome"

On Ubuntu 20.10 desktop, these important packages are among them:

gnome-control-center
gnome-session
gnome-terminal
network-manager-gnome
ubuntu-desktop
ubuntu-desktop-minimal
ubuntu-drivers-common
ubuntu-minimal
ubuntu-release-upgrader-core
ubuntu-release-upgrader-gtk
ubuntu-session
ubuntu-standard
ubuntu-system-service

Moreover, there is no such Python clean state. Each system update and each package you install might bring with it Python related dependencies.

You can however use pip or pip3 to uninstall only packages you previously manually installed and even this is not totally risk free.

If you have already removed Python, try this or this if you need a fix. Chances are little though. If you manage to fix it, you are lucky.

Golden rule... Leave the snake alone.

That being said, use a Python virtual environment for your Python projects and you shouldn't be needing to clean or go back to clean state Ubuntu system Python.

Python virtual environments create an isolated environment for your Python projects. This means that each project can have its own dependencies, regardless of what dependencies the Ubuntu system or other Python projects have.

This feature can be installed for Python3 like so:

sudo apt install python3-venv

To make a Python3 virtual environment for a project, you would first create a directory and cd to it like so:

mkdir my_env && cd my_env

Then, create a new Python3 virtual environment inside the directory like so:

python3 -m venv env

This will create a structure like this:

$tree -L 3

.
└── env
    ├── bin
    │   ├── activate
    │   ├── activate.csh
    │   ├── activate.fish
    │   ├── Activate.ps1
    │   ├── easy_install
    │   ├── easy_install-3.8
    │   ├── pip
    │   ├── pip3
    │   ├── pip3.8
    │   ├── python -> python3
    │   └── python3 -> /usr/bin/python3
    ├── include
    ├── lib
    │   └── python3.8
    ├── lib64 -> lib
    ├── pyvenv.cfg
    └── share
        └── python-wheels

To use this environment, activate it like so:

source env/bin/activate

Your shell prompt will show (env) like so:

(env) $

During this, Python3 commands, module installs or modifications will be contained locally in this virtual environment.

When you are done, deactivate this Python3 virtual environment like so:

deactivate

You are now back to the system-wide Python3 and commands will take effect globally so be careful.