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Partial recursion unrolling for PreOrderIter #278

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Partial recursion unrolling for PreOrderIter #278

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225b83b
PreOrderIter with recursion unrolling (deque)
gregreich Sep 16, 2025
1c034d2
partial recursion unrolling with list
gregreich Sep 21, 2025
34b38ee
minor changes
gregreich Sep 21, 2025
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13 changes: 10 additions & 3 deletions src/anytree/iterators/preorderiter.py
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Original file line number Diff line number Diff line change
Expand Up @@ -40,11 +40,18 @@ class PreOrderIter(AbstractIter):

@staticmethod
def _iter(children, filter_, stop, maxlevel):
for child_ in children:
cur_children = list(reversed(children))
descendantmaxlevel = maxlevel
while cur_children:
child_ = cur_children.pop()
if stop(child_):
continue
if filter_(child_):
yield child_
if not AbstractIter._abort_at_level(2, maxlevel):
descendantmaxlevel = maxlevel - 1 if maxlevel else None
if not AbstractIter._abort_at_level(2, descendantmaxlevel):
descendantmaxlevel = descendantmaxlevel - 1 if descendantmaxlevel else None
if len(child_.children) == 1:
cur_children.append(child_.children[0])
continue
yield from PreOrderIter._iter(child_.children, filter_, stop, descendantmaxlevel)
descendantmaxlevel = maxlevel
14 changes: 10 additions & 4 deletions tests/test_iterators.py
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Expand Up @@ -22,17 +22,23 @@ def test_preorder():
g = Node("g", parent=f)
i = Node("i", parent=g)
h = Node("h", parent=i)
k = Node("k", parent=a)
o = Node("o", parent=k)
m = Node("m", parent=e)

eq_(list(PreOrderIter(f)), [f, b, a, d, c, e, g, i, h])
eq_(list(PreOrderIter(f)), [f, b, a, k, o, d, c, e, m, g, i, h])
eq_(list(PreOrderIter(f, maxlevel=0)), [])
eq_(list(PreOrderIter(f, maxlevel=2)), [f, b, g])
eq_(list(PreOrderIter(f, maxlevel=3)), [f, b, a, d, g, i])
eq_(list(PreOrderIter(f, filter_=lambda n: n.name not in ("e", "g"))), [f, b, a, d, c, i, h])
eq_(list(PreOrderIter(f, stop=lambda n: n.name == "d")), [f, b, a, g, i, h])
eq_(list(PreOrderIter(f, maxlevel=4)), [f, b, a, k, d, c, e, g, i, h])
eq_(list(PreOrderIter(f, maxlevel=f.height + 1)), list(PreOrderIter(f)))
eq_(list(PreOrderIter(f, filter_=lambda n: n.name not in ("e", "g"))), [f, b, a, k, o, d, c, m, i, h])
eq_(list(PreOrderIter(f, stop=lambda n: n.name == "d")), [f, b, a, k, o, g, i, h])

it = PreOrderIter(f)
eq_(next(it), f)
eq_(next(it), b)
eq_(list(it), [a, d, c, e, g, i, h])
eq_(list(it), [a, k, o, d, c, e, m, g, i, h])


def test_postorder():
Expand Down