What is a requirements.txt file ?

Usually, a requirement file is just a list of pip install arguments. You can also specify a match version for each. Theses files can be easy install with the pip app pip install -r requirements.txt. A simple requirement file looks like:

ovh==0.4.5
requests==2.11.1
tornado==4.4.1

But for a developper, how can we generate it ? I ask me that question when I push on github my last project ExAlias. I figure that you have many solutions to do this.

1. Directly with pip

With this solution, the requirement file will contains a pinned version of everything used in the project who has been installed with pip.

$ pip freeze > requirements.txt

2. Using a third tool

The second method, (that I used) is called pipreqs. A pip requirements.txt file generator based on imports of any project.

Why using it

For 3 reasons

pip freeze only saves the packages that are installed with pip install in your environment.
pip freeze saves all packages in the environment including those that you don’t use in your current project. (if you don’t have virtualenv)
and sometimes you just need to create requirements.txt for a new project without installing modules.

how to use it

First of all, you have to install it.

$ pip install pipreqs

$ git clone https://github.com/bndr/pipreqs.git
$ cd pipreqs
$ python3 setup.py install

After that, the only thing to do is:

pipreqs Documents/project/exalias