On 4/1/2019 1:14 AM, Guido van Rossum wrote:
> We do have a parser generator in the standard library:
> https://github.com/python/cpython/tree/master/Lib/lib2to3/pgen2
It is effectively undocumented and by inference discouraged from use.
I've tried it out over the weekend. The undocumented-ness is kinda annoying but surmountable. What I found was this library is tightly coupled to the Python language, both at the lexer and parser levels. For example, defining a simple grammar like this would not work:
genericurl: scheme '://'
scheme: ...
The reason is '://' is not a known token type in Python language. That is a real bummer.
Back to my original goal, I've gathered that there is some interest in having a more general parser library in the stdlib. "Some", but not "much". Should I start out with a straw proposal so that we can hash it out further?
Cheers,
Nam
The entry for lib2to3 in the 2to3 doc:
https://docs.python.org/3/library/2to3.html#module-lib2to3
"
lib2to3 - 2to3’s library
Source code: Lib/lib2to3/
Note: The lib2to3 API should be considered unstable and may change
drastically in the future.
help(pgen) is not much more helpful.
:
Help on package lib2to3.pgen2 in lib2to3:
NAME
lib2to3.pgen2 - The pgen2 package.
PACKAGE CONTENTS
conv
driver
grammar
literals
parse
pgen
token
tokenize
FILE
c:\programs\python38\lib\lib2to3\pgen2\__init__.py
--
Terry Jan Reedy
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