simplified Python parsing question

[Eric S. Johansson]

as some folks may remember, I have been working on making Python and its tool
base more accessible to disabled programmers. I've finally come up with a really
simple technique which should solve 80% of the problem. What I need to figure
out is how to find a spot in the code where a symbol exists and potentially,
it's rough type (class name, instance, etc.). This is really a much bigger
question that I want to get into right now but I'm looking just to build a demo
to back up a storyboard plus video.

When you are sitting on or in a name, you look to the left or look to the right
what would you see that would tell you that you have gone past the end of that
name. For example

a = b + c

if you are sitting on a, the boundaries are beginning of line and =, if you are
sitting on b, the boundaries are = and +, if you are sitting on c, the
boundaries are + and end of line. a call the region between those boundaries
the symbol region.

if this example is clear to you, what you suggest for a method of finding a
whole statement, or a whole symbol region? note, doesn't have to be perfect or
complete solution, just good enough to let me do a moderately complex demo and
seek funding accessibility world to build a complete environment.

I appreciate the help because I believe that once this is working, it'll make a
significant difference in the ability for disabled programmers to write code
again as well as be able to integrate within existing development team and their
naming conventions.

Looking forward to responses.

--- eric

first draft write up of technique
https://docs.google.com/document/d/1In11apApKozw_UOPAhVz0ePqns72_6652Dra34xWp4E/edit

 

[Steven D'Aprano]

When you are sitting on or in a name, you look to the left or look to
the right what would you see that would tell you that you have gone past
the end of that name. For example

Have you read the docs? It gives full details of the Python syntax.

http://docs.python.org/reference/index.html

For example:

http://docs.python.org/reference/simple_stmts.html#assignment-statements

See also:

http://docs.python.org/library/language.html
http://effbot.org/zone/simple-top-down-parsing.htm
http://nedbatchelder.com/text/python-parsers.html


Here's a Python parser using the pyparsing library. It's a bit old
(written for Python 2.4) but it shouldn't be hard to update it to new
syntax:

http://pyparsing.wikispaces.com/file/view/pythonGrammarParser.py

 

[Eric S. Johansson]

Have you read the docs? It gives full details of the Python syntax.

Yes I have. I was hoping for a different perspective because what I'm trying to
do is middle out parsing. Top-down when the scanner focus moves from left to
right and bottom up when the scanner focus moves from right to left.

sounds kind of odd when I describe it that way but both the cursor is on the
middle of a name string and I need to look to either end of that name string
before can do a conversion to a symbol string, I have to look at both ends in
different ways. If you've read the documentation I've provided, would it be a
better example to use for describing some of the issues. Here's a very rough
draft of a storyboard

https://docs.google.com/presentation/d/1fuKyo9AE6i9ZdX2lucwK0v_W5Kx9M3Mezavm40wzCo8/edit

the first 13-14 slides are the working content for the storyboard. the rest is
mostly "memory" of things I was thinking about so if it doesn't make sense or
seems wrong, don't give me grief.

Here's a Python parser using the pyparsing library. It's a bit old
(written for Python 2.4) but it shouldn't be hard to update it to new
syntax:

http://pyparsing.wikispaces.com/file/view/pythonGrammarParser.py

thanks for the reference. I'll take a look at it as well.