Parser or regex ?

[Michael Spencer]

Fuzzyman wrote:
> Hello all,
> 
> I'm writing a module that takes user input as strings and (effectively)
> translates them to function calls with arguments and keyword
> arguments.to pass a list I use a sort of 'list constructor' - so the
> syntax looks a bit like :
> 
>    checkname(arg1, "arg 2", 'arg 3', keywarg="value",
> keywarg2='value2', default=list("val1", 'val2'))
> 
> Worst case anyway :-)
> ...

Perhaps you could simply use Python's parser - the syntax appears to be Python's.

e.g., a very quick hack using eval, which is easier without the list call, so 
I'm cheating and replacing it with a list literal for now:
  >>>
  >>> source = """checkname(arg1, "arg 2", 'arg 3', keywarg="value",
  ... keywarg2='value2', default=["val1", 'val2'])"""
  >>>

We need some way to ensure bare names don't cause NameErrors:
  >>> class lazynames(dict):
  ...     def __getitem__(self, key):
  ...         if key in self:
  ...             return dict.__getitem__(self, key)
  ...         return "%s" % key # if name not found, return it as a str constant
  ...

 >>> def checkname(*args, **kw):
  ...     return args, kw
  ...
  >>> d = lazynames(__builtins__ = None, checkname = checkname)
  >>>

With this set up, you can parse in one line!
  >>> eval(source, globals(), d)
  (('arg1', 'arg 2', 'arg 3'), {'default': ['val1', 'val2'], 'keywarg': 'value', 
'keywarg2': 'value2'})
  >>>

If you don't like the risks of eval, then compiler.parse gives a form of the 
parse output that is fairly easy to deal with

Cheers
Michael