Priority queue realization issue

[dupeljan]

BPO	42201
Nosy	@rhettinger

^{Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.}

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GitHub fields:

assignee = 'https://github.com/rhettinger'
closed_at = <Date 2020-10-31.04:23:17.911>
created_at = <Date 2020-10-30.06:40:33.995>
labels = ['type-bug', 'invalid', '3.9', 'docs']
title = 'Priority queue realization issue'
updated_at = <Date 2020-10-31.04:23:17.911>
user = 'https://bugs.python.org/dupeljan'

bugs.python.org fields:

activity = <Date 2020-10-31.04:23:17.911>
actor = 'rhettinger'
assignee = 'rhettinger'
closed = True
closed_date = <Date 2020-10-31.04:23:17.911>
closer = 'rhettinger'
components = ['Documentation']
creation = <Date 2020-10-30.06:40:33.995>
creator = 'dupeljan'
dependencies = []
files = []
hgrepos = []
issue_num = 42201
keywords = []
message_count = 2.0
messages = ['379922', '380037']
nosy_count = 3.0
nosy_names = ['rhettinger', 'docs@python', 'dupeljan']
pr_nums = []
priority = 'normal'
resolution = 'not a bug'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue42201'
versions = ['Python 3.9']

[dupeljan]

In Priority queue realization in docs https://docs.python.org/3/library/heapq.html there is no appointments that priority can be equal and the task can have different type. For example, if you store number of graph node in your priority queue, than it is possible to get "TypeError: '<' not supported between instances of 'int' and 'str'", because inside heappop there is comparison between elements, and if the fist elements the same, than it compare tasks, which can be tagged as removed and has '<removed-task>' value as opposed to number of node, which is int.

[rhettinger]

The previous example, PrioritizedItem, shows how to address the issue.