How to Use pip and requirements.txt Like a Pro (After Venv)

Hello friends, I will try as much as I can to make this brief and simple.

Outline:

1. Intro

You created a venv — great! But an empty venv does nothing. This is where pip comes in.

2. Make sure pip is using your venv

# Activate first
source venv/bin/activate  # Windows: venv\Scripts\activate
which python
pip --version

3. Installing packages

pip install requests pandas numpy
pip install requests==2.31.0  # pinned version

4. Why you need requirements.txt

Without it, anyone cloning your project won't know what to install.

5. Create it

pip freeze > requirements.txt
Example requirements.txt:

Code
numpy==1.26.0
requests==2.31.0
pandas==2.2.0
matplotlib==3.8.0

6. Install from it (on a new machine)

pip install -r requirements.txt

7. Pro Tips:

• Separate requirements-dev.txt for dev tools

• Use pip install -r requirements.txt --upgrade

• Don't manually edit versions from pip freeze unless you need to

CTA: In the next tutorial, we'll stop hardcoding API keys and use .env files.