Skip to main content

Python Virtual Env

What is a virtual environment?​

  • An isolated Python environment
  • Keeps project dependencies separate
  • Prevents breaking system Python
  • Required on modern Linux (PEP 668)

1️⃣ Create a virtual environment​

python3 -m venv venv_name(.venv)
  • venv = folder name (can be anything)
  • Creates isolated Python + pip

2️⃣ Activate the virtual environment​

Linux / macOS​

source venv_name/bin/activate

Windows​

venv_name\\Scripts\\activate

✔ Prompt shows (venv) when active

3️⃣ Deactivate the environment​

deactivate

4️⃣ Install packages (inside venv)​

pip install package_name

Example:

pip install requests PyYAML

✔ No sudo

✔ No --user

✔ No system impact

5️⃣ Check which Python / pip is used​

which python
which pip

Or:

python --version
pip --version

6️⃣ Save dependencies​

pip freeze > requirements.txt

7️⃣ Restore dependencies​

pip install -r requirements.txt

8️⃣ Remove a virtual environment​

deactivate   # if active
rm -rf venv

(No uninstall needed)

9️⃣ Common mistakes (remember this 🚨)​

❌ sudo pip install ...

❌ pip install --break-system-packages

❌ Using system Python for projects

✔ Always use a venv for projects

🔁 Typical daily workflow​

python3 -m venv venv_name
source venv_name/bin/activate
pip install -r requirements.txt
python app.py
deactivate

🧠 One-line memory trick​

Create → Activate → Install → Run → Deactivate

Bonus: Quick uv equivalent (modern)​

uv venv_name
source .venv_name/bin/activate
uv pip install requests