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Kirill Smelkov
cpython
Commits
0c3be965
Commit
0c3be965
authored
Jan 11, 2018
by
Raymond Hettinger
Committed by
GitHub
Jan 11, 2018
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bpo-31145: Use dataclasses to create a prioritization wrapper (#5153)
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02556fba
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Doc/library/heapq.rst
Doc/library/heapq.rst
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Doc/library/queue.rst
Doc/library/queue.rst
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Doc/library/heapq.rst
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0c3be965
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@@ -187,6 +187,17 @@ a tie-breaker so that two tasks with the same priority are returned in the order
they were added. And since no two entry counts are the same, the tuple
comparison will never attempt to directly compare two tasks.
Another solution to the problem of non-comparable tasks is to create a wrapper
class that ignores the task item and only compares the priority field::
from dataclasses import dataclass, field
from typing import Any
@dataclass(order=True)
class PrioritizedItem:
priority: int
item: Any=field(compare=False)
The remaining challenges revolve around finding a pending task and making
changes to its priority or removing it entirely. Finding a task can be done
with a dictionary pointing to an entry in the queue.
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Doc/library/queue.rst
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0c3be965
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@@ -56,6 +56,16 @@ The :mod:`queue` module defines the following classes and exceptions:
one returned by ``sorted(list(entries))[0]``). A typical pattern for entries
is a tuple in the form: ``(priority_number, data)``.
If the *data* elements are not comparable, the data can be wrapped in a class
that ignores the data item and only compares the priority number::
from dataclasses import dataclass, field
from typing import Any
@dataclass(order=True)
class PrioritizedItem:
priority: int
item: Any=field(compare=False)
.. exception:: Empty
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