Why doesn't python automatically install from requirements.txt?

Question

I've seen solutions which automatically install requirements.txt but nothing that says why Python doesn't have a feature for this.

Answer 1

As far as I know the requirements.txt file format has not much to do with Python itself. I believe it has been created by pip and for pip, which is a piece of software independent from Python.

If you search for requirements.txt in Python's documentation you will find only a couple of occurrences, all of them directly associated with pip. Even though pip is somehow bundled in with distributions of Python , pip is an external project.

In short: Python doesn't know anything about requirements.txt , some 3rd party tools do.

Answer 2

You have to do it like this

pip install -r /path/to/requirements.txt

Answer 3

From your comment

So what I'm asking is why can't Python see a requirements.txt file next to the script I'm running and automatically install it?

This is because Python doesn't implement this feature, which makes sense because

1. Sometimes you just want to use the locally installed packages.
2. Installing new packages takes time, disk space, bandwidth, etc.
3. Different projects may have conflicting requirements.

It's not hard to implement it yourself, by the way

alias python="if [ -f requirements.txt ]; then pip install -r requirements.txt; fi; python"