How to Auto Generate requirements.txt (Dependencies) in Python - 3 examples

John D K -

In this tutorial, we'll see how to automatically create requirements.txt in Python.

We'll cover 3 different ways of auto generation of dependencies:

  • pip freeze > requirements.txt - most generic ones. No need for additional installation.
  • dephell deps add --from=Pipfil - additional library is needed. It can generate dependencies for a single Python script
  • pipreqs /path/to/project - additional library is needed. Allow customization in order to extract requirements related to given folder

Example 1: Generate requirements.txt by pip freeze

Creating requirements.txt for a Python project with virtual environments:

pip freeze > requirements.txt

Before running the command be sure that:

  • the virtual environments is activated
  • the command will be executed in the same folder as the project

A file requirements.txt with Python dependencies will be generated in the same folder as the execution.

If you use this command all requirements will be collected from the virtual environment. If you need to get requirements used only in the current project scope then you need to check next options.

Example 2: Auto Generate requirements.txt by dephell - for a single Python script

Dephell is good option to auto generate requirements.txt if:

  • your project is not using virtual environments
  • to generate them only for a single script for a bigger Python project

More information for this package:

The dephell is installed by two options:

pip install --user dephell

or by:

curl -L dephell.org/install | python3

How to generate requirements for a single Python script? It can be done by a command:

dephell deps convert --from=my_script.py  --to=requirements.txt

Where:

  • requirements.txt is the output file
  • my_script.py is the file for which dependency list will be build

The structure of the project could be: ../project/src/my_script.py - you need to run the command from folder: src.

Another option is to use imports like:

dephell deps convert --from=imports --to=requirements.txt

Explanation is available here:

--from – path or format for reading requirements. If it is format then dephell will scan the current directory to find out a file that can be parsed by this converter. If it is filename then dephell will automatically determine file format.

Example 3: Auto Generation of requirements.txt with pipreqs

Another alternative is pipreqs. More information is available on this link: github pipreqs.

First the package needs to be installed by:

pip install pipreqs

Generating all dependencies with:

pipreqs /path/to/project

or

pipreqs /path/to/project/myfile.py

Note Why to use pipreqs? Because pip freeze will collect all dependencies from the environments. While pipreqs will collect requirements used only in the current project!

plus

  • pip freeze only saves the packages that are installed with pip install
  • pip freeze saves all packages in the environment
  • if you like to generate requirements.txt without installing the modules