Debug: Python virtual environment not activating correctly

Python virtual environment doesn't activate properly, or the wrong Python/pip is used after activation.

Diagnose venv issues:

# 1. Verify which Python is being used
which python3
which pip
python3 -c 'import sys; print(sys.executable)'
python3 -c 'import sys; print(sys.prefix)'

# 2. Check if venv is activated
echo $VIRTUAL_ENV  # Should show path to venv

# 3. Common issues:

# Issue: 'source activate' fails
# Wrong path!
source .venv/bin/activate       # Linux/macOS
source .venv/Scripts/activate   # Windows Git Bash
.venv\Scripts\activate          # Windows CMD

# Issue: Wrong Python version in venv
# Create with specific Python
python3.11 -m venv .venv  # Uses Python 3.11

# Issue: pip installs to system instead of venv
# Verify pip is from venv
pip --version  # Should show .venv path
# If not, use:
python3 -m pip install package  # Guaranteed to use venv's pip

# Issue: venv broken after Python upgrade
# Recreate the venv
rm -rf .venv
python3 -m venv .venv
source .venv/bin/activate
pip install -r requirements.txt

# Issue: IDE using wrong interpreter
# VS Code: Ctrl+Shift+P > Python: Select Interpreter
# Choose: .venv/bin/python3

# 4. Nuclear option: fresh start
deactivate 2>/dev/null
rm -rf .venv __pycache__ *.egg-info
python3 -m venv .venv
source .venv/bin/activate
pip install -r requirements.txt

Virtual environment issues usually stem from path conflicts, wrong Python version, or system Python shadowing the venv's Python.

Python development environment setup