docker-tidy/dockertidy/utils.py

#!/usr/bin/env python3
"""Global utility methods and classes."""


def strtobool(value):
    """Convert a string representation of truth to true or false."""

    _map = {
        "y": True,
        "yes": True,
        "t": True,
        "true": True,
        "on": True,
        "1": True,
        "n": False,
        "no": False,
        "f": False,
        "false": False,
        "off": False,
        "0": False
    }

    try:
        return _map[str(value).lower()]
    except KeyError as err:
        raise ValueError(f'"{value}" is not a valid bool value') from err


def to_bool(string):
    return bool(strtobool(str(string)))


def dict_intersect(d1, d2):
    return {
        k: dict_intersect(d1[k], d2[k]) if isinstance(d1[k], dict) else d1[k]
        for k in d1.keys() & d2.keys()
    }


class Singleton(type):
    """Singleton metaclass."""

    _instances = {}

    def __call__(cls, *args, **kwargs):

        if cls not in cls._instances:
            cls._instances[cls] = super().__call__(*args, **kwargs)
        return cls._instances[cls]