Master Python Virtual Environments with virtualenv and PyCharm

1. Install virtualenv

virtualenv can be installed like any other Python package, either with pip install virtualenv or by downloading the source tar.gz from the official site and running python setup.py install. Uninstall with pip uninstall virtualenv.

1.1 Install via pip

pip install virtualenv

1.2 Install from source

Download the latest tar.gz from the virtualenv website, extract it, navigate to the extracted directory, and run:

python setup.py install

2. Configure a Python virtual environment

Use virtualenv to create an isolated environment for a specific project directory, specifying the desired Python interpreter. Example for a project at c:\PythonProj\sjtu-cs using Python 3.6: virtualenv -p c:\Python36\python.exe HigEnv Here -p indicates the Python executable path, and HigEnv is the name of the virtual environment.

3. Activate the virtual environment

Activate the environment with:

c:\PythonProj\sjtu-cs>cd HigEnv\Scripts
activate

After activation, running python will use the selected Python version (e.g., print becomes a function). Deactivate with:

deactivate

4. Use virtualenv in PyCharm

PyCharm integrates virtualenv, allowing you to create or select a virtual environment directly in the IDE without manual installation.

4.1 Create a new project and choose Python version

When importing an existing project, PyCharm auto‑detects the matching Python interpreter, but you can manually select a different one.

4.2 Create a virtualenv in PyCharm

In the project settings, choose "Add New Interpreter", select "Virtualenv Environment", and specify the base interpreter (e.g., Python 3.6). PyCharm will create the environment and configure the project to use it.

You can also skip creating a new environment and simply point the project to an existing interpreter.