# Multiple Python versions

## Install Homebrew

Homebrew is a package manager for MacOS, must have CLI utility.

```
/bin/bash -c "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/HEAD/install.sh)"
```

## Install latest python

MacOS comes with a python version but you should install the latest stable version of python.

```
 brew install python
```

## Install pip

Download the `get-pip` file

```
curl https://bootstrap.pypa.io/get-pip.py -o get-pip.py
```

Now run this file to install pip

```
python get-pip.py
```

## Change global default python to latest python

```
sudo ln -s -f /usr/local/bin/python3.9 /usr/local/bin/python
```

## Install pyenv

`pyenv` makes it easy to install, manage, and switch between multiple Pythons versions.

```
brew install pyenv
```

## Install multiple python versions in pyenv

```
pyenv install 3.9.4
pyenv install 2.7.16
```

## Change default python in pyenv to latest and greatest

```
pyenv global 3.9.4
```

## Running pyenv

```
pyenv versions
python -m venv venv
source ./venv/bin/activate
(venv) $ which python
```

To exit the virtual environment

```
deactivate
```

#### References

* <https://opensource.com/article/19/6/python-virtual-environments-mac>
* [https://jacobian.org/2019/nov/11/python-environment-2020/ ](https://jacobian.org/2019/nov/11/python-environment-2020/)