Config formats

JSON and YAML

These two types are equivalent in terms of supported data types, but the author of conjector is more inclined to yaml when it comes to usability and readability. Also, yaml has such interesting things as aliases and anchors, which can simplify the work with constants even more.

However, in terms of speed, yaml loses even to the built-in json library, not to mention the faster version of ujson. Therefore, for large configurations, it is recommended to use the json format.

Also, you should keep in mind that reading configs and injecting values occurs only once at the beginning of your application, so you can neglect the performance to a certain extent.

TOML

The toml format supports all the same types as json and yaml, and since version “1.0.0”, it can work with arrays whose elements have different types. However, there is still a problem when the array contains the value null. Consider the situation when we have a variable with the following type annotation - list[int | str | None]. Then we can write it in the following ways:

1. Use the value null written as a string:

   [some_section]
   some_var = ["str", 10, "null"]
   

2. Use any invalid value (but it’s more like hack):

   [some_section]
   some_var = ["str", 10, {}]
   

INI

By default, configparser.ConfigParser doesn’t support lists and deep nested dicts, but conjector makes it possible to work with them. How does it look?

Python code:

{
    "some_key": {
        "another_key": "value",
        "deep_key": {
            "key1": True,
            "key2": None,
        }
    },
    "just_key": 10,
    "mixed_list": [10, "20", 30.5, None]
}

.ini config

[some_key]
another_key = "value"
[some_key.deep_key]
key1 = true
key2 = null
[root]
just_key = 10
mixed_list[] = 10,20,30.5,null

As you can see above, a list in a .ini config is coma-separated values where a key has a suffix [] in the end. The dict nesting is also trivial, all you need is just dot-separated keys of nested dicts in [section] part. Also, you should remember that configparser can’t work with variables without sections, so if you want to put some values in the root of a config just write a section [root] (or [ROOT]) above, like in the previous example.