Python configuration file: Any file format recommendation? INI format still appropriate? Seems quite old school

Consider using plain Python files as configuration files.

An example (config.py):

# use normal python comments

value1 = 32
value2 = "A string value"

value3 = ["lists", "are", "handy"]
value4 = {"and": "so", "are": "dictionaries"}

In your program, load the config file using exec (docs):

from pathlib import Path

if __name__ == "__main__":
    config = {}
    exec(Path("config.py").read_text(encoding="utf8"), {}, config)
    
    print(config["value1"])
    print(config["value4"])

I like this approach, for the following reasons:

• In the simple case, the format is as easy to author as an INI-style config file. It also shares an important characteristic with INI files: it is very suitable for version control (this is less true for XML and maybe also for JSON)
• I like the flexibility that comes with having the config file in an actual programming language.

The approach is widely used, a few examples:

• A Django site’s settings lives inside settings.py. Django does not use execfile, it uses import to read/execute settings.py AFAIK, but the end result is the same: the code inside the settings file is executed.
• The bash shell reads and executes ~/.bashrc on startup.
• The Python interpreter imports site.py on startup.