In 2022, If you're building an application and are looking for a simple answer, just use Poetry; it's similar enough to what you'll be familiar with if coming from other languages (e.g. yarn, cargo, ...). For most usecases you can just lean on Poetry's venv management; you don't need to do more than `poetry shell` or `poetry run` to get access to it. Poetry will create, and for the most part manage, your pyproject.toml file for you.

If you want a bit more flexibility Virtualenv is part of python now (`python -m venv`). If you're on MacOS you can get great venv management with pyenv and pyenv-virtualenv. And for sure, things get more complex if you're building a library. But I think Poetry is a solid place to start.