Class _UnhashDict

lib/matplotlib/cbook.py:147–199

A minimal dict-like class that also supports unhashable keys, storing them in a list of key-value pairs. This class only implements the interface needed for `CallbackRegistry`, and tries to minimize the overhead for the hashable case.

class _UnhashDict:
    """
    A minimal dict-like class that also supports unhashable keys, storing them
    in a list of key-value pairs.

    This class only implements the interface needed for `CallbackRegistry`, and
    tries to minimize the overhead for the hashable case.
    """

    def __init__(self, pairs):
        self._dict = {}
        self._pairs = []
        for k, v in pairs:
            self[k] = v

    def __setitem__(self, key, value):
        try:
            self._dict[key] = value
        except TypeError:
            for i, (k, v) in enumerate(self._pairs):
                if k == key:
                    self._pairs[i] = (key, value)
                    break
            else:
                self._pairs.append((key, value))

    def __getitem__(self, key):
        try:
            return self._dict[key]
        except TypeError:
            pass
        for k, v in self._pairs:
            if k == key:
                return v
        raise KeyError(key)

    def pop(self, key, *args):
        try:
            if key in self._dict:
                return self._dict.pop(key)
        except TypeError:
            for i, (k, v) in enumerate(self._pairs):
                if k == key:
                    del self._pairs[i]
                    return v
        if args:
            return args[0]
        raise KeyError(key)

    def __iter__(self):
        yield from self._dict
        for k, v in self._pairs:
            yield k


class CallbackRegistry: