# Adding dependencies per "Packaging Python Projects"

**URL:** <https://discuss.python.org/t/adding-dependencies-per-packaging-python-projects/14048>\
**Category:** Packaging\
**Created:** [March 3, 2022, 9:30pm UTC](https://discuss.python.org/t/adding-dependencies-per-packaging-python-projects/14048 "2022-03-03T21:30:15Z")\
**Posts on this page:** 10\
**Page:** 1

<div class="post-metadata">

**Author:** ![rockobonaparte](https://avatars.discourse-cdn.com/v4/letter/r/8baadc/32.png) [@rockobonaparte](https://discuss.python.org/u/rockobonaparte)\
**Post date:** [March 3, 2022, 9:30pm UTC](https://discuss.python.org/t/adding-dependencies-per-packaging-python-projects/14048/1 "2022-03-03T21:30:15Z")

</div>

Regarding [Packaging Python Projects — Python Packaging User Guide](https://packaging.python.org/en/latest/tutorials/packaging-projects/)

This is a pretty basic problem of just properly expressing dependencies.

I can adapt that tutorial to build a package for a project on which I’m working. The problem is that I haven’t figured out how to declare dependencies. I’ve tried a few things that all didn’t work so instead I figured I’d just ask here what is actually correct.

I was testing it by installing it into an empty virtualenv, and then running pip freeze in that environment to verify whether or not it was there. The only thing that shows up after installing is the package itself that I installed.

I am betting there are multiple ways to do it based on whatever. In my case, it’s rather simple: I just need json5 \>= 0.9.6.

I’m also hoping something about dependencies can be put in that tutorial.

---

<div class="post-metadata">

**Author:** ![merwok](https://sea2.discourse-cdn.com/flex002/user_avatar/discuss.python.org/merwok/32/29_2.png) [@merwok](https://discuss.python.org/u/merwok)\
**Post date:** [March 3, 2022, 9:54pm UTC](https://discuss.python.org/t/adding-dependencies-per-packaging-python-projects/14048/2 "2022-03-03T21:54:49Z")

</div>

The key word is _dependencies_, also called _requirements_.  
If you are following the guide and using setuptools as a build tool, the info is here: [Packaging and distributing projects — Python Packaging User Guide](https://packaging.python.org/en/latest/guides/distributing-packages-using-setuptools/#install-requires)  
Personally I find flit quite nice for simple projects (pure Python, no C extensions): [The pyproject.toml config file — Flit 3.7.1 documentation](https://flit.readthedocs.io/en/latest/pyproject_toml.html#dependencies)

---

<div class="post-metadata">

**Author:** ![rockobonaparte](https://avatars.discourse-cdn.com/v4/letter/r/8baadc/32.png) [@rockobonaparte](https://discuss.python.org/u/rockobonaparte)\
**Post date:** [March 3, 2022, 10:19pm UTC](https://discuss.python.org/t/adding-dependencies-per-packaging-python-projects/14048/3 "2022-03-03T22:19:31Z")

</div>

I’m trying to join the cool kids who are not using setup.py any more and I thought that tutorial I posted was about the newer packaging conventions. It looks like the documentation you sent was for using a setup.py and the install\_requires is being listed as an argument to the setup() function.

Do I actually still need to use a setup.py if I have requirements?

---

<div class="post-metadata">

**Author:** ![jwodder](https://sea2.discourse-cdn.com/flex002/user_avatar/discuss.python.org/jwodder/32/236_2.png) [@jwodder](https://discuss.python.org/u/jwodder)\
**Post date:** [March 3, 2022, 10:31pm UTC](https://discuss.python.org/t/adding-dependencies-per-packaging-python-projects/14048/4 "2022-03-03T22:31:00Z")

</div>

> [@rockobonaparte](#):
>
> Do I actually still need to use a setup.py if I have requirements?

No. If you’re using setuptools, you can specify the requirements in `setup.cfg`:

```auto
[options]
install_requires =
    json5 >= 0.9.6

```

---

<div class="post-metadata">

**Author:** ![merwok](https://sea2.discourse-cdn.com/flex002/user_avatar/discuss.python.org/merwok/32/29_2.png) [@merwok](https://discuss.python.org/u/merwok)\
**Post date:** [March 3, 2022, 10:33pm UTC](https://discuss.python.org/t/adding-dependencies-per-packaging-python-projects/14048/5 "2022-03-03T22:33:07Z")

</div>

The new cool thing is that we can have multiple installation frontend (pip, tox, etc) working with multiple build backends (setuptools, flit, etc). Setuptools is not shunned, it’s just demoted from its position as preferred tool that defines most of the experience and the de facto interface with pip. A project needs some config in `pyproject.toml` (to wire the build backend to frontends) and some other config in another section of that file or another file entirely depending on the build backend.

The guide you linked uses setuptools, so you should follow the setuptools docs guide I linked to add dependencies to your config file (setup.cfg or setup.py).

---

<div class="post-metadata">

**Author:** ![CAM-Gerlach](https://sea2.discourse-cdn.com/flex002/user_avatar/discuss.python.org/cam-gerlach/32/3688_2.png) [@CAM-Gerlach](https://discuss.python.org/u/CAM-Gerlach)\
**Post date:** [March 3, 2022, 11:04pm UTC](https://discuss.python.org/t/adding-dependencies-per-packaging-python-projects/14048/6 "2022-03-03T23:04:24Z")

</div>

> [@rockobonaparte](#):
>
> I was testing it by installing it into an empty virtualenv, and then running pip freeze in that environment to verify whether or not it was there. The only thing that shows up after installing is the package itself that I installed.

FYI, `pip list` is the command to run to see what’s currently installed in your environment.

> [@rockobonaparte](#):
>
> The only thing that shows up after installing is the package itself that I installed.

Presumably, the dependency wasn’t listed under the appropriate key for listing run-time requirements for your chosen build backend (e.g. `install_requires` under `[metadata]` in `setup.cfg` for Setuptools, `dependencies` under `[project]` in `pyproject.toml` for the new format specified in [PEP 621](https://www.python.org/dev/peps/pep-0621/)).

If you only listed your dependencies in a `requirements.txt` file, it will not be installed automatically. The use of `requirements.txt` files (often generated by `pip freeze` or `pip-tools`) is generally for manual installation for development and applications that need to reproduce a given environment exactly, or other specialized applications, and must be manually specified by e.g. `pip install -r requirements.txt`.

> [@jwodder](#):
>
> > [@rockobonaparte](#):
> >
> > Do I actually still need to use a setup.py if I have requirements?
> 
> No. If you’re using setuptools, you can specify the requirements in `setup.cfg` :

To elaborate, in reasonably recent versions of Setuptools, you can [decoratively specify your metadata and build config in a static setup.cfg](https://setuptools.pypa.io/en/stable/userguide/declarative_config.html). This is simpler, much harder to mess up and has many benefits over using a dynamic `setup.py` file for the same purpose, and [tools exist](https://github.com/asottile/setup-cfg-fmt) to convert the latter to the former. While in recent-enough Setuptools you can omit the `setup.py` completely, its probably best to retain a stub setup.py for now, e.g.

```python
#!/usr/bin/env python3

"""Stub setup.py for use with legacy build tooling."""

import setuptools

if __name__ == " __main__":
    setuptools.setup()

```

to accommodate legacy tooling and use cases.

Furthermore, forthcoming versions of Setuptools will gain support for specifying dependencies in the PEP 621-specified `[project]` table of `pyproject.toml`, which will work with _any_ build backend (Flit, Setuptools, Poetry, PDM, Hatch, etc) once they support it (which with Setuptools adding support, leaves Poetry as the main laggard here).

```ini
[project]
dependencies = [
    "json5 >= 0.9.6",
]

```

> [@Help testing experimental features in setuptools](https://discuss.python.org/t/help-testing-experimental-features-in-setuptools/13821):
>
> Hello all. For the past months we have been experimenting with adding some features to setuptools, specially the support for project metadata in pyproject.toml (initially introduced in PEP 621). Other features complement it: automatic layout discovery (for flat, src or single-module layouts), defaulting to include\_package\_data=True, etc… The idea is to make the [tool.setuptools] table in pyproject.toml not necessary that for the simple use cases. If anyone is interested in helping testing the…

---

<div class="post-metadata">

**Author:** ![rockobonaparte](https://avatars.discourse-cdn.com/v4/letter/r/8baadc/32.png) [@rockobonaparte](https://discuss.python.org/u/rockobonaparte)\
**Post date:** [March 4, 2022, 5:43pm UTC](https://discuss.python.org/t/adding-dependencies-per-packaging-python-projects/14048/7 "2022-03-04T17:43:32Z")

</div>

Thanks in particular to John’s response, I was able to figure out how to get the json5 requirement into the package metadata.

I also added a legacy setup.py as recommended. I actually think I need that to satisfy a goofy, internal back end we are using.

A lot of my confusion regarding these methods comes from stumbling into the new pattern with a project.toml and everything else when investigating a random setuptools bug that had happened a few months ago. From that correspondence, I had found out about the new paradigm. So when I had to make a new Python package, I decided to look it up in more detail and found the tutorial I was using.

The tutorial was still deferring to setuptools. It’s not that I need or want to use it. I’m trying to figure out what I should be doing to get ahead of the standard changes. So if there are additional steps I should be taking that I’ll want to get that out of the way here too. The situation I’m working on right now is what I’d consider to be a simplified, yet still typical one so it’s a decent place to learn the new conventions.

---

<div class="post-metadata">

**Author:** ![CAM-Gerlach](https://sea2.discourse-cdn.com/flex002/user_avatar/discuss.python.org/cam-gerlach/32/3688_2.png) [@CAM-Gerlach](https://discuss.python.org/u/CAM-Gerlach)\
**Post date:** [March 4, 2022, 7:11pm UTC](https://discuss.python.org/t/adding-dependencies-per-packaging-python-projects/14048/8 "2022-03-04T19:11:53Z")

</div>

> [@rockobonaparte](#):
>
> I’m trying to figure out what I should be doing to get ahead of the standard changes. So if there are additional steps I should be taking that I’ll want to get that out of the way here too.

Basically, to summarize, if you’re using Setuptools the de-facto current packaging setup is as follows:

- `pyproject.toml` → build system config (boilerplate from the packaging guide)
- `setup.cfg` → Primary metadata and Setuptools configuration (e.g. deps, metadata, options, etc)
- `setup.py` → Stub file for legacy tooling (boilerplate from above)

Once Setuptools support for metadata and configuration in `pyproject.toml` lands and stabilize, and tools that don’t support the new modern standards have been retired, or if you switch to another build system like `flit` that already does, this can be reduced to just a `pyproject.toml` with build system + metadata + setuptools config (what was previously in setup.cfg). You’ll want to make sure you require a minimum version of setuptools in the build system config that supports `pyproject.toml` metadata and config.

---

<div class="post-metadata">

**Author:** ![barry](https://sea2.discourse-cdn.com/flex002/user_avatar/discuss.python.org/barry/32/42_2.png) [@barry](https://discuss.python.org/u/barry)\
**Post date:** [March 5, 2022, 1:46am UTC](https://discuss.python.org/t/adding-dependencies-per-packaging-python-projects/14048/9 "2022-03-05T01:46:36Z")

</div>

> [@CAM-Gerlach](#):
>
> if you’re using Setuptools the de-facto current packaging setup is as follows

This is one of the things I love about PDM (and similar package managers): I really _only_ need a `pyproject.toml`.

---

<div class="post-metadata">

**Author:** ![CAM-Gerlach](https://sea2.discourse-cdn.com/flex002/user_avatar/discuss.python.org/cam-gerlach/32/3688_2.png) [@CAM-Gerlach](https://discuss.python.org/u/CAM-Gerlach)\
**Post date:** [March 5, 2022, 2:02am UTC](https://discuss.python.org/t/adding-dependencies-per-packaging-python-projects/14048/10 "2022-03-05T02:02:40Z")

</div>

> [@barry](#):
>
> > [@CAM-Gerlach](#):
> >
> > if you switch to another build system like `flit` that already does, this can be reduced to just a `pyproject.toml`
> 
> This is one of the things I love about PDM (and similar package managers): I really _only_ need a `pyproject.toml` .

Yep—if we’re getting into tool recommendations, flit is a great tool for users developing library-type projects that want something that simplifies the process as much as practical while doing all the “right things” for them. But really, as you say, any of the modern PEP 517 backends are a good choice if you’re not (and don’t want to be) bound by supporting all the legacy ways of doing things.