On Thu, Jun 13, 2019 at 12:52 AM Yanghao Hua <[email protected]> wrote:
>
> On Wed, Jun 12, 2019 at 11:27 PM Chris Angelico <[email protected]> wrote:
> > Yes, you would need some sort of syntactic parser. There are a couple
> > of ways to go about it. One is to make use of Python's own tools, like
> > the ast module; the other is to mandate that your specific syntax be
> > "tidier" than the rest of the Python code, which would permit you to
> > use a more naive and simplistic parser (even a regex).
>
> Yep ... I just tried to use MacroPy3 to handle this but failed, seems
> MacroPy3 does expect valid Python syntax in the first place for
> anything else to happen. I also tried the raw ast module which seems
> also the case. So it means if one want to use python ast module to
> parse user input, the user input has to be valid python syntax (e.g.
> no <==) at the first place. Seems this is a chicken-egg problem.
Attaching the trace:
Traceback (most recent call last):
File "tt.py", line 34, in <module>
main()
File "tt.py", line 8, in main
tree = ast.parse(source.read())
File "/usr/lib/python3.6/ast.py", line 35, in parse
return compile(source, filename, mode, PyCF_ONLY_AST)
File "<unknown>", line 1
x <== 3
^
SyntaxError: invalid syntax
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