Source code for molfoundry.isotope

from .exceptions import LogicError




class Isotope:
    """Representation of the isotope of an atom.

    The value is either the "most abundant" sentinel ``-1`` or a concrete mass
    number ``>= 1``.
    """

    def __init__(self, isotope: int = -1):
        if isotope != -1 and isotope < 1:
            raise LogicError(
                f"Invalid isotope {isotope}: must be -1 (most abundant) or >= 1."
            )
        self._isotope = isotope

    def __int__(self) -> int:
        return self._isotope

    def __str__(self) -> str:
        return str(self._isotope)

    def __eq__(self, other: object) -> bool:
        if isinstance(other, Isotope):
            return self._isotope == other._isotope
        if isinstance(other, int):
            return self._isotope == other
        return NotImplemented

    def __hash__(self) -> int:
        # Defining ``__eq__`` otherwise makes the type unhashable; hash on the
        # underlying value so an Isotope and the equal plain int hash alike.
        return hash(self._isotope)