bpo-31145: Use dataclasses to create a prioritization wrapper (#5153) · python/cpython@0c3be96 (original) (raw)

2 files changed

lines changed

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@@ -187,6 +187,17 @@ a tie-breaker so that two tasks with the same priority are returned in the order
187	187	they were added. And since no two entry counts are the same, the tuple
188	188	comparison will never attempt to directly compare two tasks.
189	189
	190	+Another solution to the problem of non-comparable tasks is to create a wrapper
	191	+class that ignores the task item and only compares the priority field::
	192	+
	193	+ from dataclasses import dataclass, field
	194	+ from typing import Any
	195	+
	196	+ @dataclass(order=True)
	197	+ class PrioritizedItem:
	198	+ priority: int
	199	+ item: Any=field(compare=False)
	200	+
190	201	The remaining challenges revolve around finding a pending task and making
191	202	changes to its priority or removing it entirely. Finding a task can be done
192	203	with a dictionary pointing to an entry in the queue.

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@@ -56,6 +56,16 @@ The :mod:`queue` module defines the following classes and exceptions:
56	56	one returned by ``sorted(list(entries))[0]``). A typical pattern for entries
57	57	is a tuple in the form: ``(priority_number, data)``.
58	58
	59	+ If the data elements are not comparable, the data can be wrapped in a class
	60	+ that ignores the data item and only compares the priority number::
	61	+
	62	+ from dataclasses import dataclass, field
	63	+ from typing import Any
	64	+
	65	+ @dataclass(order=True)
	66	+ class PrioritizedItem:
	67	+ priority: int
	68	+ item: Any=field(compare=False)
59	69
60	70	.. exception:: Empty
61	71