90% workflow – one time setup per project

# 1. Create (most people name it .venv)
python -m venv .venv

# 2. Activate it
# macOS / Linux / git-bash / WSL
source .venv/bin/activate

# Windows (Command Prompt or PowerShell)
.venv\Scripts\activate

# You'll see (.venv) in your prompt

# 3. Always upgrade pip first
python -m pip install --upgrade pip

# 4. Install your project packages
pip install fastapi uvicorn python-dotenv pytest httpx

# When finished → just type:
deactivate
# or close the terminal

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One-liner favorites (Linux/macOS)

python -m venv .venv && source .venv/bin/activate && python -m pip install --upgrade pip