Operator precedence documentation could be more clear

[aidanfeldman]

BPO	43837
Nosy	@gvanrossum, @rhettinger, @terryjreedy, @stevendaprano, @cjerdonek, @zware, @gvanrossum, @ammaraskar, @miss-islington
PRs	bpo-43837: Reverse order of precedence table to show tightly binding operators first #25469 [3.9] bpo-43837: Reverse order of precedence table to show tightly binding operators first (GH-25469) #25472

^{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 = None
closed_at = <Date 2021-04-19.16:10:14.928>
created_at = <Date 2021-04-14.04:38:05.832>
labels = ['type-feature', '3.9', '3.10', 'docs']
title = 'Operator precedence documentation could be more clear'
updated_at = <Date 2021-04-19.16:10:14.927>
user = 'https://bugs.python.org/aidanfeldman'

bugs.python.org fields:

activity = <Date 2021-04-19.16:10:14.927>
actor = 'rhettinger'
assignee = 'none'
closed = True
closed_date = <Date 2021-04-19.16:10:14.928>
closer = 'rhettinger'
components = ['Documentation']
creation = <Date 2021-04-14.04:38:05.832>
creator = 'aidan.feldman'
dependencies = []
files = []
hgrepos = []
issue_num = 43837
keywords = ['patch']
message_count = 12.0
messages = ['391030', '391044', '391106', '391107', '391259', '391260', '391361', '391362', '391364', '391381', '391384', '391385']
nosy_count = 11.0
nosy_names = ['gvanrossum', 'rhettinger', 'terry.reedy', 'steven.daprano', 'chris.jerdonek', 'docs@python', 'zach.ware', 'Guido.van.Rossum', 'ammar2', 'miss-islington', 'aidan.feldman']
pr_nums = ['25469', '25472']
priority = 'normal'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'enhancement'
url = 'https://bugs.python.org/issue43837'
versions = ['Python 3.9', 'Python 3.10']

[aidanfeldman]

I am teaching a class on Python for people who are new to coding, and I was talking them through the operator precedence table:

https://docs.python.org/3/reference/expressions.html#operator-precedence

A couple things that confused the students:

• "Highest precedence" is on the bottom, while "lowest precedence" is on top
• There isn't any mention of variables. While not operators, probably worth mentioning that they (effectively?) have higher precedence than any of the operators.

I'd be happy to try making my first contribution to Python if there's interest in those edits. Also, I have an example breaking down operator precedence in practice here, which I could include:

https://colab.research.google.com/github/afeld/python-public-policy/blob/main/lecture_2.ipynb#scrollTo=UTxeT5RvqSFl

Thanks!

[stevendaprano]

There isn't any mention of variables. While not operators, probably worth mentioning that they (effectively?) have higher precedence than any of the operators.

I'm sorry, I don't understand what that means.

[aidanfeldman]

Let me try and say a simpler way: I think "variables" should be mentioned in that section, either in the table or the paragraph above.

[zware]

I think it might be easiest to see your suggestion as a pull request :)

[terryjreedy]

When I looked at the table yesterday (after several years), I was initially confused at the 'reversed' order (before I checked the text above). Besides precedence usually (nearly always) being listed high to low*, the chapter itself is highest to lowest, so the table is reversed from the chapter order.

• I checked K&R C and several sites and images and all I saw had highest at the top (highest). This include other Python charts.

The table has been this way since at least 1.4
https://docs.python.org/release/1.4/ref/ref5.html#HDR18
Guido, how would you feel about reversing it to follow what seems to be the de facto standard?

The header 'Operator' could be changed to 'Operator (lowest first)' but I would prefer to make that 'Operator (highest first)'.