One post tagged with "virtual-environments"

As a technical writer working extensively with Python-based documentation tools like Sphinx, I rely heavily on virtual environments to isolate dependencies and keep my projects reproducible.

One mistake I made early on—and one I see others make too—is trying to copy or migrate the entire virtual environment folder (venv) from one location to another.

It seems convenient, but it’s a trap. Let me walk you through why this doesn’t work reliably, what actually breaks, and how to fix it the right way.

The Problem: Copying the venv Folder Breaks Path Bindings​

When you create a virtual environment using:

python -m venv venv

Python generates a folder named venv (or whatever name you choose) that contains:

• The Python interpreter binaries
• Scripts for activating the environment
• A pyvenv.cfg file with absolute paths
• Site-packages and installed dependencies

The issue? The pyvenv.cfg file and internal scripts contain hardcoded absolute paths to the original Python executable and environment location. If you move the folder to a different directory or machine, those paths become invalid.

Example: pyvenv.cfg Contents​

home = C:\Users\Me\AppData\Local\Programs\Python\Python311
include-system-site-packages = false
version = 3.11.4

If you copy the venv folder to a new location, say D:\Projects\NewSite\venv, the activation scripts and interpreter references will still point to the old path. On Windows, this often results in cryptic errors when trying to activate or run Python from the environment.

The Hack: Rewriting pyvenv.cfg​

Some developers try to manually edit pyvenv.cfg and update the home path. While this can work in very limited cases, it’s not reliable. The activation scripts (activate, activate.bat, activate.ps1) and internal symlinks may still break, especially across operating systems or Python versions.

The Right Way: Recreate the Virtual Environment​

Here’s the clean, reproducible workflow I now follow for every Sphinx documentation project:

1. Create a requirements.txt or pyproject.toml​

Before migrating, freeze your dependencies:

pip freeze > requirements.txt

Or use a modern tool like Poetry to manage dependencies via pyproject.toml.

2. Delete the Old venv Folder​

rm -r venv  # macOS/Linux
rmdir /S /Q venv  # Windows

3. Recreate the Environment in the New Location​

python -m venv venv

4. Reinstall Dependencies​

# macOS/Linux
source venv/bin/activate

# Windows
venv\Scripts\activate

pip install -r requirements.txt

Or if using Poetry:

poetry install

Bonus Tip: Use .venv for Consistency​

Many tools (like Poetry and VS Code) look for a .venv folder in the project root. Naming your environment .venv keeps things tidy and avoids cluttering your workspace.

Summary​

Final Thoughts​

Virtual environments are essential for clean Python workflows, especially in documentation projects where reproducibility matters. But they’re not portable in the way you might expect. Rebuilding them is fast, reliable, and avoids the headaches of broken paths and activation errors.