How to Create Requirements.txt File in Python

Creating and maintaining a requirements.txt file is a fundamental best practice for Python development. It ensures that your project's dependencies are well-documented and easily reproducible, making it easier for others to work on your code and reducing the likelihood of compatibility issues.

Why Use a requirements.txt File?

A requirements.txt file serves several important purposes:

• Reproducibility: By specifying the exact versions of packages and libraries your project depends on, you ensure that anyone else working on your project can create the same environment and reproduce the same results.
• Dependency Management: Managing dependencies becomes more manageable. You can easily add, update or remove packages as needed without keeping track of them manually.
• Compatibility: It helps avoid version conflicts between packages, ensuring that all dependencies work together harmoniously.
• Deployment: When deploying your application or sharing it with others, you can provide them with a requirements.txt file to install the necessary dependencies effortlessly.

Steps to Create a requirements.txt File

Step 1: Set up a virtual environment

Using a virtual environment isolates your project’s dependencies, preventing conflicts with system-wide Python packages.

• Open a terminal and navigate to your project directory.
• Create and activate a virtual environment using the following commands.

# Create a virtual environment
python -m venv myenv

# Activate the virtual environment

# on Windows
myenv\Scripts\activate

# on macOS and Linux
source myenv/bin/activate

Step 2: Install Dependencies

Install the necessary dependencies for your project using pip. Replace package-name with the actual package you want to install.

pip install package-name

For example, to install pandas:

pip install pandas

Step 3: Generate the requirements.txt File

Once all required packages are installed, generate the requirements.txt file by running:

pip freeze > requirements.txt

This command captures all installed dependencies and their versions in the file.

Step 4: Review your requirement.txt file

After generating the file, review its contents using :

cat requirements.txt

It should list installed packages with their versions, like:

pandas==1.5.3

numpy==1.23.5

Step 5: Install dependencies from requirement.txt

When setting up the project on a new system, install all dependencies using:

pip install -r requirements.txt

This ensures that all required packages are installed with the specified versions.

Best Practices for Managing requirements.txt

• Regularly Update Dependencies: Periodically update the file by running pip freeze > requirements.txt after adding new packages.
• Pin Package Versions: Specify exact versions to avoid compatibility issues (e.g., numpy==1.23.5 instead of numpy).
• Use a Separate Dev Requirements File: Maintain a dev-requirements.txt for development dependencies like testing tools.
• Use Virtual Environments: Always create and use a virtual environment to manage dependencies efficiently.