Map a function to the leafs of a mapping.

def map_leafs(func, mapping):
    """Map a function to the leafs of a mapping."""

    def _inner(mapping, path=None):
        if path is None:
            path = []

        for key, val in mapping.items():
            if isinstance(val, collections.Mapping):
                _inner(val, path + [key])
            else:
                mapping[key] = func(val, path=path+[key])

        return mapping

    return _inner(copy.deepcopy(mapping))