How to Install Python Packages with Requirements.txt

Managing Python dependencies is easy with requirements.txt. This file lists all packages your project needs. Learn how to use it.

What is requirements.txt?

A requirements.txt file contains a list of Python packages. Each package has a version number. This helps recreate the same environment.

It ensures everyone uses the same dependencies. This avoids conflicts and errors. It's a best practice for Python projects.

Creating a requirements.txt File

First, install the packages you need. Use pip install for each package. Then, generate the file.

 
pip install package1 package2 package3
pip freeze > requirements.txt

This creates requirements.txt in your project folder. Open it to see the installed packages.

Installing Packages from requirements.txt

Use pip install -r to install all listed packages. Run this command in your project directory.

 
pip install -r requirements.txt

This installs all dependencies. It ensures your project runs smoothly.

Example of requirements.txt

Here’s an example of a requirements.txt file:

 
numpy==1.21.0
pandas==1.3.0
requests==2.26.0

Each line specifies a package and version. This ensures consistency across setups.

Updating requirements.txt

Update the file when you add new packages. Use pip freeze again to refresh it.

 
pip freeze > requirements.txt

This overwrites the old file. Always check the changes before committing.

Handling Different Environments

Use separate files for different environments. For example, dev-requirements.txt for development.

This keeps production clean. Only necessary packages are installed there.

Common Issues and Fixes

Sometimes, installation fails. Check these common issues:

1. Wrong Python version: Ensure compatibility.

2. Network issues: Check your internet connection.

3. Package not found: Verify the package name.

For more help, check our guide on How to Install Tkinter in Python.

Using Virtual Environments

Virtual environments isolate dependencies. Create one using python -m venv.

 
python -m venv myenv
source myenv/bin/activate  # On Linux/Mac
myenv\Scripts\activate  # On Windows

This avoids conflicts between projects. Always activate it before installing packages.

Advanced Usage

You can specify versions flexibly. For example:

 
package>=1.0.0  # Minimum version
package<=2.0.0  # Maximum version
package~=1.2.0  # Compatible release

This gives more control over dependencies. Learn more in our Install Paramiko in Python Easily guide.

Conclusion

Using requirements.txt simplifies dependency management. It ensures consistency across setups.

Always update it when adding new packages. Use virtual environments for isolation. For more tips, see Install Python Package from Local Directory.

Now you can manage Python packages like a pro!