In the python reference manual, section 5.9,
all that stuff with italic "opa", "opb" etc
reads rather poorly because of a visually confusing
choice of names.

The bit about "...then a opa b opb c ... y opy z opz"
looks more like "aopabopbcopc...yopyzopz" : in other
words a unintelligible string of gibberish.   A similar
problem occurs slightly below.

Note that the spaces *are* really there, but they do not show up well in the italic font used on my Firefox/Debian system, so it's hard to parse.
The visual confusion is exacerbated by the similarities
in the operator and variable names (e.g. "opa" and "a",
then "opb" then "b"), and also by the use of a three-character string to mean "operator a" versus a
one-character name for the variable.

So, please change "opa" to "A" et cetera, or make some
other change that makes it easier to read.