confuk 0.9.4

Yet another configuration loading package for Python projects

Confuk

This is yet another package for managing configuration files in Python projects.

It exposes one function that lets you provide a path to a TOML/YAML/JSON configuration file. It parses the config file into a dictionary by default. If a config class is provided when parsing, the class instance will be created using a dictionary of keyword arguments coming from the original TOML/YAML/JSON file.

In human words: I made this package so that I don't have to explicilty load, parse and return a class instance every single time I have something to do with a configuration file:

from confuk import parse_config
from pathlib import Path
from somewhere import ConfigClass

cfg_dict = parse_config(Path("some.toml"))  # returns a dictionary
cfg_obj = parse_config(Path("some.toml"), ConfigClass)  # returns an instance of `ConfigClass`

[!tip] confuk also supports a number of output configuration styles out-of-the-box, including omegaconf, Pydantic and EasyDict.

Installation

pip install confuk

Or:

poetry add confuk

Building from source

You can build the package using Poetry:

1. Clone this repo.
2. Run poetry build.
3. Grab the installable wheel from the dist folder and install it with pip or add the package as a local dependency of another project.

Special features

Config output formats

EasyDict

If you really hate referring to dictionary keys and you do not intend to create a custom configuration class for your config, you can parse the file to an EasyDict:

cfg_edict = parse_config(Path("some.toml"), "attr")

Now, if the key something exists in the configuration file, you can simply refer to it using an attribute:

cfg_edict.something

OmegaConf

OmegaConf is one of the most complete configuration systems for Python applications. If you want to leverage its features while still working with confuk as a front-end, you can simply parse the configuration into an instance of omegaconf.DictConfig by doing the following:

cfg = parse_config(Path("some.toml"), "omega")

Pydantic

If you're a fan of Pydantic with custom config classes for automatic validation, just use any class that inherits from BaseModel:

from confuk import parse_config
from pathlib import Path
from pydantic import BaseModel

class Metrics(BaseModel):
    psnr: float
    ssim: float


cfg_dict = parse_config(Path("some.toml"), Metrics)  # returns a dictionary

All currently supported formats

Format	cfg_class argument
dict	"d" / None
EasyDict	"ed" / "edict" / "attr"
OmegaConf	"o" / "omega" / "omegaconf"
pydantic	BaseModel class
custom	any class supporting **kwargs in the constructor

Imports

Because keeping hundreds of config files can become tedious, especially when there is shared values between them, you might want to consider using the imports functionality.

Say you have a TOML file from which you want to inherit values:

[something]
value = 1
another_value = 2

[something_else]
value = 3

You can "import" it using a preamble:

[pre]
imports = [
    "${this_dir}/test_imported.toml",
]

[something]
value = 69

[!note] Older versions of confuk used the $this_dir syntax instead. This will be supported going into the future but it won't work with variable interpolation (expect it to only work for the special interpolation markers such as $this_dir and $cwd).

This is equivalent to specifying a config like:

[something]
value = 69
another_value = 2

[something_else]
value = 3

Note that you can use several special interpolation markers to specify paths in the import section:

• ${this_dir} -> points to a directory relative to the configuration file that contains the import section
• ${cwd} -> points to the current working directory
• ${this_filename} -> config filename (with extension)
• ${this_filename_stem} -> filename without the extension (stem)
• ${this_dirname} -> the name of the directory where the configuration file lives (not a path)
• ${this_filename_suffix} -> suffix (without the dot) of the current configuration file

[!warning] The preamble will be removed after it's processed. It's there only to control how confuk should process the loaded configuration files and it's dropped afterwards. Do not put any meaningful configuration into your preamble, except for confuk's control elements.

Lazy interpolation

By default the interpolation markers like ${this_filename} will interpolate the current file name. So if for example you create a.yaml and it contains:

pre:
  imports:
    - b.yaml

And b.yaml contains:

filename: "${this_filename}"

Then filename will be b.yaml. This is expected as these markers are interpolated as-is in the file they were found in.

[!important] If you want to defer the interpolation of these markers to happen in the final config file, use $[] markers instead.

So for example if you change b.yaml to contain:

filename: "$[this_filename]"

Then filename will be **a.yaml** if you have called parse_config on the a.yaml file.

What about inheriting selected values?

Unsupported. And I do not plan to add support for cherrypicking values from other configs. It makes things way messier in my opinion, as it becomes way harder to reason about the flow of variables.

As far as accessing other values within imported config, read the next section – that is supported via OmegaConf.

What about variable interpolation?

This is supported with the syntax that OmegaConf uses, e.g. path = "${some.root.path}/file.txt" will pick up the path variable from some.root config section. The interpolation markers that I mentioned in the Imports section should also work anywhere else within the config, so you can use your ${this_filename_stem} to refer to config names within the config itself. One use-case is when you want to have subdirectories in a results directory, where you would silo away the results from different configs:

results_dir = "results/${this_filename_stem}"

Assumming that you have 3 configs for your experiments: ex1, ex2 and ex3, you could instead put results_dir in a parent config to all those:

# to_import.toml:
results_dir = "results/${this_filename_stem}"

# ex1
[pre]
imports = ["${this_dir}/to_import.toml"]
a_variable_that_diverges_across_configs = 69

# ex2
[pre]
imports = ["${this_dir}/to_import.toml"]
a_variable_that_diverges_across_configs = 420

# ex3
[pre]
imports = ["${this_dir}/to_import.toml"]
a_variable_that_diverges_across_configs = 42

[!note] We are using omegaconf for all other interpolation tasks under the hood since they already have a great parser for this and there's no use duplicating work.

What about deeply nested configs?

If you like the deeply nested folder-file structure for your configs then Hydra might be more for you. I've used it before and it's very good but I personally find the design choice of creating directory structures for configs quite tedious.

confuk strives to be flatter: you import another config file in the preamble section and you have a choice of what to override. This makes it more comfortable to use when you have one default.toml config file for something and then create a bunch of configurations overriding certain values. This is useful for experiments in the AI/ML space, where I'm spending most of my time now.

You are of course free to structure your files as you please but don't expect a feature similar to Hydra's defaults in confuk – I do indeed use Hydra for applications which require such a system!

Command-line overrides

One of the most fantastic features I've found when using Hydra was the ability to override values from the config file on the command line. This is convenient when you want to quickly test some changes to your configuration without going through the trouble of creating a new config file.

So I concluded it would be fun to implement it in confuk in a similar fashion. Here's how it works:

import confuk


@confuk.main(config=Path(__file__).parent / "test.toml", config_format="o", verbose=False)
def main(cfg, *args):
    console = Console()
    console.print(cfg)
    return cfg

This decorator behaves similarly to @hydra.main decorator and it creates a minimal argument parser for your application entrypoint under the hood.

Now, when running the app, you can specify any value overrides on the command line. For example if your config looks like this:

[my]
mother = 1

[your.dad]
father = 1

And you run your CLI app with the argument your.dad.father=3, you will override the pertinent value from 1 to 3.

[!tip] The underlying argument parser also contains a --config option. You can use it to switch to a different config path on the command line, without a need to rely on the default one that has been set in the decorator.

Dumping configs

This is mostly for debugging purposes.

Sometimes, when you use a lot of imports it might be hard to figure out what is the final config form after all the imports have been resolved. Starting from version 0.8.0 you can now dump your configs to JSON, YAML, TOML, Pickle and JSONPickle and the routing is done using file extensions:

• *.json – dump to JSON
• *.yaml – dump to YAML
• *.toml – dump to TOML
• *.jsonp – dump to JSONPickle
• *.pkl – dump to Pickle

To perform the dumping just use:

from confuk import dump_config

dump_config(cfg, "some_cfg.json")

[!warning] Not all types in your config object might be serializable, especially if you're using custom classes. When loading a config using omegaconf adapter, we're ensuring that the output is serialized properly, with other config backends it might not be so pretty at the moment. If you're running into trouble my suggestion is to dump to a Pickle and use something like objexplore to load the Pickle back again and explore the contents of the constructed config.

Config file documentation

When designing a config file, you will often want to also document what each property means. Sadly enough, there aren't that many packages which handle config documentation very well. This is partially due to limitations of file formats used for configuration. For example YAML and TOML specifications do not cover parsing comments, meanwhile a lot of folks out there use comments to document parts of their config files:

apple:
  # Color of the apple
  color: red
  # Size of the apple
  size: medium

We thought of implementing parsing for these but seriously, who would have time to build a reliable new parser for YAML or TOML which also processes comments correctly? Instead, it was much simpler to go with a separate documentation file. For the example above, you would create another file, e.g. config.doc.yaml:

apple:
  _doc_: properties of an apple
  color:
    _doc_: Color of the apple
  size:
    _doc_: Size of the apple

Then you can simply run:

confuk doc ./config.doc.yaml

This will display the documentation in the console, paged for your pleasure of reading. You have currently the following alternative options to display the contents of the documentation:

• confuk doc ./config.doc.yaml -f test.html – as an HTML file (append -o to open it in the web browser right away)
• confuk doc ./config.doc.yaml -t – in a tree view (might be more helpful for figuring out complex hierarchies)

Parsing configs on the command line

Because sometimes you might want to display the cumulative config files after the imports and interpolations have been resolved, we added as an alternative to dumping to a file a command-line based print of the collected config:

confuk parse <path-to-config>