Separating Development and Production Dependencies

It says “Run ‘make lib’ to install these dependencies in this project’s lib directory” in the requirements.txt file. Is this another way to restore Captured Dependencies? How does it works? Thank you :D

Whenever you have a make <target_name> command in a project you can typically look up the definition of the that make command in a text-based configuration file called Makefile.

So what this make lib makefile command does is most likely just calling pip install with a list of requirements or a requirements file.

When you open the Makefile included with your project you’ll probably see something like this:

lib:
    pip install -r requirements.txt

It’ll (very likely) just call the pip command behind the scenes to handle the actual Python dependency install :)

Here’s more info on the make command and makefiles: en.wikipedia.org/wiki/Makefile

Two observations / questions (with sub questions) at this point:

1. You detailed the slick pip freeze built-in workflow to get the requirements.txt and requirements-dev.txt. However, does one keep separate dev and production projects to do this, or is there a way of keeping two-in-one (dev and prod) and then “filtering” the freeze? (And if two separate, how are they kept synchronized?)

2. “freeze” captures only the 3rd party dependency tree but how does one specify the root Python distribution that must be used? (I know some who re-translated a bunch of v2.x code by hand… if they had known the content of this course maybe they wouldn’t have needed to do such :) )

@Zarata You can combine multiple requirements files using the -r flag inside one of them. For example, consider the following two files:

$ cat requirements.txt
requests==2.24.0
click==7.1.2
Flask==1.1.2

$ cat -r requirements-dev.txt
-r requirements.txt
bpython==0.20
pytest==6.1.1

When you install the development requirements, it’ll automatically install all the production ones too:

$ pip install -r requirements-dev.txt
Collecting requests==2.24.0
  Using cached requests-2.24.0-py2.py3-none-any.whl (61 kB)
Collecting click==7.1.2
  Using cached click-7.1.2-py2.py3-none-any.whl (82 kB)
Collecting Flask==1.1.2
  Using cached Flask-1.1.2-py2.py3-none-any.whl (94 kB)
Collecting bpython==0.20
  Using cached bpython-0.20-py2.py3-none-any.whl (189 kB)
Collecting pytest==6.1.1
  Using cached pytest-6.1.1-py3-none-any.whl (272 kB)
(...)

To lock third-party dependency versions and specify a particular Python interpreter, you can take advantage of Pipenv or poetry.

Could you please tell me why I received the Error for installing requirements-dev.txt? I went through following steps:

$ pip install requests
$ pip freeze  requests
$ pip freeze > requirements.txt
$ pip install -r requirements-dev.txt
ERROR: Could not open requirements file: [Errno 2] No such file or directory: 'requirements-dev.txt'

You’re getting the error because you haven’t created your requirements-dev.txt file yet. You did make a requirements.txt. If you want to freeze your dependencies to your dev file, then you should use:

$ pip freeze > requirements-dev.txt

Hope that makes sense.

That is the point, you are right. I appreciate your prompt support so much.