argparse-dataclasses 0.1.4

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argparse_dataclasses

In this package we'll place some boilerplate code that helps:

• to convert dataclasses to argparse commandline argument parsers;
• to convert argparse commandline arguments to dataclasses.

Why so?

Dozens of times I had to create settings classes for my Python console scripts. Here's some utility boilerplate code that helps to create commandline parsers for dataclasses in a couple of lines = )

How to install

python3 -m pip install argparse-dataclasses

How to use

At first, let's create a simple script simple_example.py, in which we:

• import some stuff from our module,
• declare a simple dataclass
• and inherit it from our CmdParsingMixin (this adds support for automatic argparse.ArgumentParser creation.

simple_example.py

from dataclasses import dataclass, field
from argparse_dataclasses import CmdParsingMixin


@dataclass
class SimpleSettings(CmdParsingMixin): #
    name: str
    num_experiments: int = field(default=1)


settings = SimpleSettings.build_from_commandline()

print(settings)  # That's all, folks!

And let's run this script from commandline:

    $ python3 simple_example.py

It will give us the error message.

    usage: simple_example.py [-h] --name NAME [--num-experiments NUM_EXPERIMENTS]
    simple_example.py: error: the following arguments are required: --name

Okay, just as planned. As we can see, we've forgot a required commandline argument. Let's try again

    $ python3 simple_example.py --name=DJ_BLYATMAN --num-experiments=33

This will print us the settings instance:

SimpleSettings(name='DJ_BLYATMAN', num_experiments=33)

Be careful: use - in commandline argument names and _ in Python dataclass field names. It does make sense!

Our code works with argparse.ArgumentParser under the hood, so it also supports --help commandline argument to explicitly order help message:

    $ python3 simple_example.py --help

It will output the following:

usage: simple_example.py [-h] --name NAME [--num-experiments NUM_EXPERIMENTS]

Creating SimpleSettings instance from commandline args...

optional arguments:
  -h, --help            show this help message and exit
  --name NAME
  --num-experiments NUM_EXPERIMENTS