When neither Poetry nor PyEnv should be used, you can set up a [standalone virtualenv](https://docs.python.org/3/library/venv.html) for your project:
```shell
python3 -m venv .venv # default path: .venv in $CWD
```
And then use it:
```shell
source .venv/bin/activate
```
Stop using it with `deactivate`