mirrors/cpython
1
0
Fork 0
mirror of https://github.com/python/cpython.git synced 2025-08-27 04:05:34 +00:00
Code Issues Projects Releases Packages Wiki Activity Actions 8

gh-130914: Make graphlib.TopologicalSorter.prepare() idempotent (#131317)

Browse source 
Closes #130914: Make graphlib.TopologicalSorter.prepare() idempotent

Relax the rules so that `.prepare()` can be called multiple times, provided that no work has been passed out by `.get_ready()` yet.
This commit is contained in:
Daniel Pope 2025-03-18 21:28:00 +00:00 • committed by GitHub
parent f819900245
commit c1b42db9e4
No known key found for this signature in database
GPG key ID: B5690EEEBB952194
6 changed files with 44 additions and 7 deletions
Download patch file Download diff file Expand all files Collapse all files

16
Lib/graphlib.py
View file

@ -90,13 +90,17 @@ class TopologicalSorter:
still be used to obtain as many nodes as possible until cycles block more
progress. After a call to this function, the graph cannot be modified and
therefore no more nodes can be added using "add".
"""
if self._ready_nodes is not None:
raise ValueError("cannot prepare() more than once")
self._ready_nodes = [
i.node for i in self._node2info.values() if i.npredecessors == 0
]
Raise ValueError if nodes have already been passed out of the sorter.
"""
if self._npassedout > 0:
raise ValueError("cannot prepare() after starting sort")
if self._ready_nodes is None:
self._ready_nodes = [
i.node for i in self._node2info.values() if i.npredecessors == 0
]
# ready_nodes is set before we look for cycles on purpose:
# if the user wants to catch the CycleError, that's fine,
# they can continue using the instance to grab as many