started operations

pyproject.toml

@@ -54,7 +54,7 @@ select = [
     "SIM", # flake8-simplify
 ]
 extend-fixable = ["ALL"]
-ignore = ["UP046"]
+ignore = ["UP046", "UP047"]
 
 [tool.ruff.lint.isort]
 known-first-party = ["daglib"]

src/daglib/dag.py

@@ -5,9 +5,9 @@ from collections.abc import Callable, Iterable, Iterator, MutableMapping
 from dataclasses import dataclass, field
 from typing import Generic, TypeVar
 
+from .operations import transitive_closure
 from .set import DAGSetView
-
+from .typing import dictset
-type dictset = defaultdict[T, set[T]]
 
 T = TypeVar("T")
 
@@ -115,3 +115,13 @@ class DAG(Generic[T], MutableMapping[T, DAGSetView[T]]):
 
         self._succ.pop(u, None)
         self._pred.pop(u, None)
+
+    def subgraph(self, sub: Iterable[T]) -> dictset[T]:
+        closure = transitive_closure(self, sub)
+        subgraph = DAG[T]()
+        for n, deps in self._succ.items():
+            if n in closure:
+                subgraph[n] += deps & closure
+        subgraph.on_add = self.on_add
+        subgraph.on_remove = self.on_remove
+        return subgraph

src/daglib/operations.py

@@ -0,0 +1,43 @@
+from __future__ import annotations
+
+from collections.abc import Iterable
+from typing import TYPE_CHECKING, Any, TypeVar
+
+from .util import ensure_set
+
+if TYPE_CHECKING:
+    from .dag import DAG
+    from .typing import dictset
+
+T = TypeVar("T")
+
+
+def all_nodes(graph: DAG) -> set:
+    return set(graph.keys()) | set(graph.reverse.keys())
+
+
+def transitive_closure(graph: DAG[T], sub: T | Iterable[T], *, include_self: bool = False):
+    sub = ensure_set(sub)
+    stack = list(sub)
+    seen = set()
+
+    while stack:
+        n = stack.pop()
+        if n in seen:
+            continue
+        seen.add(n)
+        stack.extend(graph.get(n, []))
+
+    if include_self:
+        seen.update(sub)
+
+    return seen
+
+
+def slice_subgraph(graph: DAG, sub: Any) -> dictset:
+    closure = transitive_closure(graph, sub)
+    return {n: d & closure for n in closure if (d := set(graph[n]))}
+
+
+def topological_sort(graph: DAG, *, reverse: bool = False) -> list:
+    return list(graph.keys())

src/daglib/typing.py

@@ -0,0 +1,10 @@
+from __future__ import annotations
+
+from collections import defaultdict
+from collections.abc import MutableMapping, MutableSet
+from typing import TypeVar
+
+T = TypeVar("T")
+
+type dictset = defaultdict[T, set[T]]
+type DAGType = MutableMapping[T, MutableSet[T]]

tests/test_dag.py

@@ -301,6 +301,7 @@ class TestDAGComplexScenarios:
         g["foo"] -= {"bar"}
         assert len(g["foo"]) == 2
         assert "bar" not in g["foo"]
+        assert set(g["foo"]) == {"baz", "d"}
 
     def test_type_hints_with_ints(self) -> None:
         g = DAG[int]()