init_attrs_with_kwargs

A helper for type-checked command-line argument store.

init_args_with_kwargs enables to store the command line arguments (positioned arguments and options) parsed with docopt in an object of a typed class.

Sample

from init_attrs_with_kwargs import cast_set_attrs

class MyArgs:
    count: int
    name: str
    max_length: int

# Initialize from docopt's return value, with casting str to int
args = cast_set_attrs(MyArgs(), **{'<count>': '1', '--name': "Joe", '--max-length': '100'})

print("args.count=%s" % repr(args.count))
print("args.name=%s" % repr(args.name))
print("args.max_length=%s" % repr(args.max_length))

Another samples:

• sample1.py. Describes data type conversion and error handling.
• sample2.py. Storing docopt-parsed command line arguments in a type-hinted class's object.
• sample3.py. Handling command and optional argument.

Motivation

I like to use docopt to design command lines. With docopt, I can design a command line in a vague state at first, and then I can make it more and more concrete and detailed.

As a recent trend in Python coding, you can also use type hints for code completion in text editors such as VSCode. Here's the problem: since the result of docopt parsing is a dict, you will be accessing, for example, args["name"], and the editor's completion will not work. Similarly, you cannot benefit from static type checking with type hints.

This issue can be solved by converting a docopt dict into an object of a typed class. init_attrs_with_kwargs is a helper just for this purpose.

Links

• (PyPI page of) init_attrs_with_kwargs https://pypi.org/project/init-attrs-with-kwargs/

• docopt https://pypi.org/project/docopt/

• type-docopt, which introduces type declaration, and holds arguments/options in dict. https://pypi.org/project/type-docopt/