Class TargetVars

pythonwhat/parsing.py:24–64

Immutable ordered mapping from target variables to their values.

class TargetVars(Mapping):
    """Immutable ordered mapping from target variables to their values."""

    EMPTY = EmptyTargetVar()

    def __init__(self, target_vars=tuple(), is_empty=True):
        if is_empty:
            target_vars = [(v, self.EMPTY) for v in target_vars]

        self._od = OrderedDict(target_vars)

    # getitem, len, iter wrap OrderedDict behavior
    def __getitem__(self, k):
        return self._od.__getitem__(k)

    def __len__(self):
        return self._od.__len__()

    def __iter__(self):
        return self._od.__iter__()

    def update(self, *args, **kwargs):
        cpy = self.copy()
        cpy._od.update(*args, **kwargs)
        return cpy

    def copy(self):
        return self.__class__(self._od)

    def __str__(self):
        """Format target vars for printing"""
        if len(self) > 1:
            return "({})".format(", ".join(self._od.keys()))
        else:
            return "".join(self._od.keys())

    def defined_items(self):
        """Return copy of instance, omitting entries that are EMPTY"""
        return self.__class__(
            [(k, v) for k, v in self.items() if v is not self.EMPTY], is_empty=False
        )


class IndexedDict(Mapping):