JezK
Edit File: structs.py
import itertools from .compat import collections_abc class DirectedGraph(object): """A graph structure with directed edges.""" def __init__(self): self._vertices = set() self._forwards = {} # <key> -> Set[<key>] self._backwards = {} # <key> -> Set[<key>] def __iter__(self): return iter(self._vertices) def __len__(self): return len(self._vertices) def __contains__(self, key): return key in self._vertices def copy(self): """Return a shallow copy of this graph.""" other = DirectedGraph() other._vertices = set(self._vertices) other._forwards = {k: set(v) for k, v in self._forwards.items()} other._backwards = {k: set(v) for k, v in self._backwards.items()} return other def add(self, key): """Add a new vertex to the graph.""" if key in self._vertices: raise ValueError("vertex exists") self._vertices.add(key) self._forwards[key] = set() self._backwards[key] = set() def remove(self, key): """Remove a vertex from the graph, disconnecting all edges from/to it.""" self._vertices.remove(key) for f in self._forwards.pop(key): self._backwards[f].remove(key) for t in self._backwards.pop(key): self._forwards[t].remove(key) def connected(self, f, t): return f in self._backwards[t] and t in self._forwards[f] def connect(self, f, t): """Connect two existing vertices. Nothing happens if the vertices are already connected. """ if t not in self._vertices: raise KeyError(t) self._forwards[f].add(t) self._backwards[t].add(f) def iter_edges(self): for f, children in self._forwards.items(): for t in children: yield f, t def iter_children(self, key): return iter(self._forwards[key]) def iter_parents(self, key): return iter(self._backwards[key]) class IteratorMapping(collections_abc.Mapping): def __init__(self, mapping, accessor, appends=None): self._mapping = mapping self._accessor = accessor self._appends = appends or {} def __repr__(self): return "IteratorMapping({!r}, {!r}, {!r})".format( self._mapping, self._accessor, self._appends, ) def __bool__(self): return bool(self._mapping or self._appends) __nonzero__ = __bool__ # XXX: Python 2. def __contains__(self, key): return key in self._mapping or key in self._appends def __getitem__(self, k): try: v = self._mapping[k] except KeyError: return iter(self._appends[k]) return itertools.chain(self._accessor(v), self._appends.get(k, ())) def __iter__(self): more = (k for k in self._appends if k not in self._mapping) return itertools.chain(self._mapping, more) def __len__(self): more = sum(1 for k in self._appends if k not in self._mapping) return len(self._mapping) + more class _FactoryIterableView(object): """Wrap an iterator factory returned by `find_matches()`. Calling `iter()` on this class would invoke the underlying iterator factory, making it a "collection with ordering" that can be iterated through multiple times, but lacks random access methods presented in built-in Python sequence types. """ def __init__(self, factory): self._factory = factory def __repr__(self): return "{}({})".format(type(self).__name__, list(self._factory())) def __bool__(self): try: next(self._factory()) except StopIteration: return False return True __nonzero__ = __bool__ # XXX: Python 2. def __iter__(self): return self._factory() class _SequenceIterableView(object): """Wrap an iterable returned by find_matches(). This is essentially just a proxy to the underlying sequence that provides the same interface as `_FactoryIterableView`. """ def __init__(self, sequence): self._sequence = sequence def __repr__(self): return "{}({})".format(type(self).__name__, self._sequence) def __bool__(self): return bool(self._sequence) __nonzero__ = __bool__ # XXX: Python 2. def __iter__(self): return iter(self._sequence) def build_iter_view(matches): """Build an iterable view from the value returned by `find_matches()`.""" if callable(matches): return _FactoryIterableView(matches) if not isinstance(matches, collections_abc.Sequence): matches = list(matches) return _SequenceIterableView(matches)