Microsoft site says "GetVersionEx may be altered or unavailable for releases after Windows 8.1. Instead, use the Version Helper functions"
VersionHelpers.h has "IsWindows10CreatorsOrGreater()" function for checking Windows 10 Build 15063+ and has "IsWindows10AnniversaryOrGreater()" function for checking Windows 10 Build 14393+.
It are official functions.

A Python core developer has requested some changes be made to your pull request before we can consider merging it. If you could please address their requests along with any other requests in other reviews from core developers that would be appreciated.

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Earlier versions of Windows 10 SDK don't have IsWindows10CreatorsOrGreater() function, people will get a build failure with those Win 10 SDK.
I'm thinking a workaround, any ideas?

Offical VersionHelpers.h doesn't have IsWindows10CreatorsOrGreater() and IsWindows10AnniversaryOrGreater() functions.

The two functions are available in a third part VersionHelpers.h, which using a DDK interface RtlGetVersion(...) to get version infomation.

Now I'm inclined to patch in socket.py again, although sys.getwindowsversion() is also using GetVersionEx(...) in underlying level. At least, it keeps socketmodule.c neat.
A code block like this solves the problem:

if hasattr(sys, 'getwindowsversion'):
    # (new_option, available_build)
    # make sure the list ordered by available_build descendent
    _new_flags = [
        ('TCP_KEEPIDLE',  16299),  # Windows 10 1709
        ('TCP_KEEPINTVL', 16299),
        ('TCP_KEEPCNT',   15063),  # Windows 10 1703
        ('TCP_FASTOPEN',  14393)   # Windows 10 1607
        ]
    _WIN_MAJOR, _WIN_MINOR, _WIN_BUILD, *_ = sys.getwindowsversion()
    
    if _WIN_MAJOR == 10 and _WIN_MINOR == 0:
        for _flag, _build in _new_flags:
            if _WIN_BUILD < _build:
                if hasattr(_socket, _flag):
                    delattr(_socket, _flag)
            else:
                break
    elif _WIN_MAJOR < 10:
        for _flag, _ in _new_flags:
            if hasattr(_socket, _flag):
                delattr(_socket, _flag)

This PR is prepared for review.

Official VersionHelpers.h uses VerifyVersionInfo(...) function in the inner side.
I'm also using VerifyVersionInfo(...), but made it aware of BuildNumber.

This PR is conflicts with 3.6 branch code.
PR 5585 is prepared for 3.6 branch, besides code conflict, the only difference is that PR 5585 can't recognize the two flags (TCP_KEEPIDLE,TCP_KEEPINTVL) added in 1709 SDK.

@zware
Forgive me for my verdant of GitHub.
This morning I pushed a minor commit, after that, I found there was a message:

zware dismissed their stale review 9 hours ago
Comment addressed; not qualified for full review.

But I can't found any comment, this make me feel very embarrassed.
So if you had addressed a comment, could you please post it again?

Look just above the message from @bedevere-bot for my old review comment, which was just formalization of the comment left by @skn78 and which you have addressed already.

I'm afraid that's about the extent of my ability to review this one, though.

ok

I have modified, sorry for my unskillful patch.

Thanks @animalize for the PR, and @zooba for merging it 🌮🎉.. I'm working now to backport this PR to: 3.6, 3.7.
🐍🍒⛏🤖

GH-5910 is a backport of this pull request to the 3.7 branch.

Sorry, @animalize and @zooba, I could not cleanly backport this to 3.6 due to a conflict.
Please backport using cherry_picker on command line.
cherry_picker 19e7d48ce89422091f9af93038b9fee075d46e9e 3.6

GH-5585 is a backport of this pull request to the 3.6 branch.

Thanks @animalize!