Initialize attributes with keyword arguments (license: Public Domain https://creativecommons.org/publicdomain/zero/1.0/deed)

Initialize_attributes_with_keyword_arguments_test.py

# a revised and unit-tested version has been published at https://github.com/tos-kamiya/init_attrs_with_kwargs

from typing import get_type_hints
from enum import Enum


class InitAttrsWKwArgs:
    @staticmethod
    def _convert_option_name_to_attr_name(name: str) -> str:
        if name.startswith('--'):
            ns = name[2:]
        elif name.startswith('-'):
            ns = name[1:]
        elif name.startswith('<') and name.endswith('>'):
            ns = name[1:-1]
        else:
            ns = name
        ns = ns.replace('-', '_')
        
        if not(len(ns) > 0 and ('a' <= ns[0] <= 'z' or 'A' <= ns[0] <= 'Z') and \
                all('a' <= c <= 'z' or 'A' <= c <= 'Z' or '0' <= c <= '9' or c == '_' for c in ns)):
            assert False, "the name does not seem either option or positional argument: %s" % repr(name)

        return ns
    
    def __init__(self, _cast_str_values=False, **kwargs):
        attr_to_type = get_type_hints(self.__class__)
        for name in kwargs:
            attr = InitAttrsWKwArgs._convert_option_name_to_attr_name(name)
            t = attr_to_type.get(attr)
            assert t is not None, "attribute not found: %s" % attr
            v = kwargs[name]
            if _cast_str_values and isinstance(v, str):
                try:
                    if issubclass(t, bool):
                        v = not not v
                    elif issubclass(t, int):
                        v = int(v)
                    elif issubclass(t, float):
                        v = float(v)
                    elif issubclass(t, Enum):
                        v = t[v]  # conversion from str to Enum (it might not look so)
                except TypeError:
                    pass  # issubclass raises a TypeError for Union, etc.
            setattr(self, attr, v)


class Hoge(InitAttrsWKwArgs):
    count: int
    name: str
    max_length: int


# Initialize from docopt's return value (dict).
v1: Hoge = Hoge(**{'<count>': 1, '--name': "Joe", '--max-length': 100})

print("dir(v1)=%s" % repr(dir(v1)))
print("v1.count=%s" % repr(v1.count))
print("v1.name=%s" % repr(v1.name))
print("v1.max_length=%s" % repr(v1.max_length))

# Initialize with keyword argument.
v2: Hoge = Hoge(count=10, name='Jane', max_length=99)

print("dir(v2)=%s" % repr(dir(v2)))
print("v2.count=%s" % repr(v2.count))
print("v2.name=%s" % repr(v2.name))
print("v2.max_length=%s" % repr(v2.max_length))

# Initialize from docopt's return value, with casting str to int
v3: Hoge = Hoge(_cast_str_values=True, **{'<count>': '1', '--name': "Joe", '--max-length': '100'})

print("dir(v3)=%s" % repr(dir(v3)))
print("v3.count=%s" % repr(v3.count))
print("v3.name=%s" % repr(v3.name))
print("v3.max_length=%s" % repr(v3.max_length))