add almost equal operator

gistfile1.txt

diff --git a/Grammar/Grammar b/Grammar/Grammar
index 170518af74..25067147bf 100644
--- a/Grammar/Grammar
+++ b/Grammar/Grammar
@@ -138,7 +138,7 @@ not_test: 'not' not_test | comparison
 comparison: expr (comp_op expr)*
 # <> isn't actually a valid comparison operator in Python. It's here for the
 # sake of a __future__ import described in PEP 401 (which really works :-)
-comp_op: '<'|'>'|'=='|'>='|'<='|'<>'|'!='|'in'|'not' 'in'|'is'|'is' 'not'
+comp_op: '<'|'>'|'=='|'>='|'<='|'<>'|'!='|'~='|'in'|'not' 'in'|'is'|'is' 'not'
 star_expr: '*' expr
 expr: xor_expr ('|' xor_expr)*
 xor_expr: and_expr ('^' and_expr)*
diff --git a/Grammar/Tokens b/Grammar/Tokens
index 9de2da5d15..c2451f3964 100644
--- a/Grammar/Tokens
+++ b/Grammar/Tokens
@@ -53,6 +53,7 @@ ATEQUAL                 '@='
 RARROW                  '->'
 ELLIPSIS                '...'
 COLONEQUAL              ':='
+ALMOSTEQUAL             '~='

So, I think there are three problems with the current version cpython-internals-2020-06-03.pdf and the adding of the almost equal operator

• not mentioning to add ALMOSTEQUAL '~=' to Grammar/Tokens
• usage of make regen-all (which produces this pyconfig.h problem) instead of make regen-grammar
• not mentioning to start python as ./python -X oldparser

On page 117 there seems to be another problem - it is written...

Now recompile CPython and open up a REPL to test the command:
>>> a = 1
>>> b = 1.0
>>> a ~= b
True

But further down you can read, that "At this stage, the tokenizer and the AST can parse this code, but the
compiler won’t know how to handle the operator. "

So, I guess, the above snippet should be deleted here - and you just have to compile Python, but do not try the almost equal operator on the REPL - or do.. a funny XKCD message is shown.