On Wed, Oct 23, 2019, 4:31 PM Steven D'Aprano 
David, you literally wrote the book on text processing in Python. I think you are being disingenious here, and below when you describe a standard string hex-escape \x20 that has been in Python forever and in just about all C-like languages as "weird".

I'm so flattered anyone remembers that from long ago. It was a very fun book to write. :-)

I think, however, that I've never written '\x20' before this moment in my life. I do know the ASCII and Unicode code point for a space. I've run the 'hexdump' utility plenty of times. But it's hard to think of an occasion when I would have needed to enter a space by code point rather than just quoted.

So I don't think it's so disingenuous to think needing to do that would be "weird." I've escaped lots of other characters that don't have a giant key about 7x the width of other keys on my keyboard.

If you can understand why this works:
    string = "Single\n quoted\n string\n containing newlines!"
you can understand the burnt\x20umber example.

I can discern your intention for the new behavior, yes.  But:

In [2]: "burnt\x20umber".split()
Out[2]: ['burnt', 'umber']
In [3]: "Single\n quoted\n string\n containing newlines!".split()
Out[3]: ['Single', 'quoted', 'string', 'containing', 'newlines!']

So this new syntax would behave in a way that is counter-intuitive for folks familiar with Python strings to date.

Also, I genuinely am not clear what should happen if an expression like

%w[cyan   forest green  burnt\x20umber]

Contains any of the following (non-escaped) characters. If they occur inside quotes, it seems straightforward, but in this new '%w[]' thing, who knows?

U+00A0 NO-BREAK SPACE foo bar As a space, but often not adjusted
U+1680 OGHAM SPACE MARK foo bar Unspecified; usually not really a space but a dash
U+2000 EN QUAD foo bar 1 en (= 1/2 em)
U+2001 EM QUAD foo bar 1 em (nominally, the height of the font)
U+2002 EN SPACE (nut) foo bar 1 en (= 1/2 em)
U+2003 EM SPACE (mutton) foo bar 1 em
U+2004 THREE-PER-EM SPACE (thick space) foo bar 1/3 em
U+2005 FOUR-PER-EM SPACE (mid space) foo bar 1/4 em
U+2006 SIX-PER-EM SPACE foo bar 1/6 em
U+2007 FIGURE SPACE foo bar “Tabular width”, the width of digits
U+2008 PUNCTUATION SPACE foo bar The width of a period “.”
U+2009 THIN SPACE foo bar 1/5 em (or sometimes 1/6 em)
U+200A HAIR SPACE foo bar Narrower than THIN SPACE
U+200B ZERO WIDTH SPACE foobar 0
U+202F NARROW NO-BREAK SPACE foo bar Narrower than NO-BREAK SPACE (or SPACE), “typically the width of a thin space or a mid space”
U+3000 IDEOGRAPHIC SPACE foo bar The width of ideographic (CJK) characters.