List Python Packages That Will Be Installed From Requirements.txt

In my requirements.txt I have packages defined in following manner: Django ~= 2.2.0 It means that when I use pip install -r requirements.txt pip will find the latest available 2.2

Solution 1:

pip-compile is what you need! Doc: https://github.com/jazzband/pip-tools)

python -m pip install pip-tools
pip-compile requirements.txt --output-file requirements-all.txt

The pip-compile command lets you compile a requirements.txt file from your dependencies, this way you can pip install you dependencies to always have the same environment

Solution 2:

TL;DR

Try pipdetree or pip-tree.

Explanation

pip, contrary to most package managers, doesn't have a big dependency graph to look up. What it does is that it lets arbitrary setup code to be executed, which automatically pulls the dependencies. This means that, for example, a package could manage their dependencies in an other way than putting them in requirements.txt (see fastai for an example of a project that handles the dependencies differently).

So, there is, theoretically, no other way to see all the dependencies than to actually run an install on an isolated environment, see what was pulled, then delete the environment (because it could potentially be the same part of the code that does the installation and that brings the dependencies). You could actually do that with venv.

In practice, tools like pipdetree or pip-tree fetch the dependencies based on some standardization of the requirements (most packages separate the dependencies and the installation, and actually let pip handle both).