Hi Gregor,
Maybe the module traceback could help you here.
It has same functions to extract the actual stack of the program.
HTH Ewald
Gregor Lingl wrote:
> Hi all,
>
> I've a class with a lot of methods, for which I'd like to check argument
> types.
> To show you, what I mean, I've written a prototype I'm not really content
> with.
> It goes like this (a bit revised in order to have short codelines (*mail*
> ;-)):
>
> class BadArgError(Exception):
> def __init__(self, fname, var, typ, val):
> self.fname = fname
> self.var = var
> self.typ = typ
> self.val = val
> def __str__(self):
> return """
> %s: argument %s must be %s!
> %s of %s given.""" % ( self.fname, self.var,
> self.typ, repr(self.val), type(self.val))
>
> def checkargs(fun,locs,*typelist):
> varnames=fun.im_func.func_code.co_varnames[1:]
> fn = fun.__name__
> for var, typ in zip(varnames, typelist):
> ok = isinstance(locs[var],typ)
> if not ok:
> raise BadArgError(fn, var, typ, locs[var])
>
> ## classe for testing:
>
> class Z(object):
> pass
>
> class A(object):
> def f(self,x,y):
> checkargs(self.f, locals(), int, str)
> def g(self,a,b,c):
> checkargs(self.g, locals(), (int,float), Z, tuple)
>
>
> BadArgError works like this (interactive session):
>
> >>> bae = BadArgError("myfun", "myvar", str, 3)
> >>> raise bae
>
> Traceback (most recent call last):
> File "<pyshell#5>", line 1, in -toplevel-
> raise bae
> BadArgError:
> myfun: argument myvar must be <type 'str'>!
> 3 of <type 'int'> given.
>
> You see, I want to the error-message to display the name of the function,
> which
> got the bad argument, the name of the parameter and it's expected type as
> well
> as the wrong argument.
>
> Examples for it's use:
>
> >>> z=Z()
> >>> a=A()
> >>> a.f(1,"a") #ok
> >>> a.f(1,2)
>
> Traceback (most recent call last):
> File "<pyshell#9>", line 1, in -toplevel-
> ...<snip>
> raise BadArgError(fn, var, typ, locs[var])
> BadArgError:
> f: argument y must be <type 'str'>!
> 2 of <type 'int'> given.
> >>> a.g(.5, z, ()) #ok
> >>> a.g(.5, a, ())
>
> Traceback (most recent call last):
> File "<pyshell#11>", line 1, in -toplevel-
> ...<snip>
> raise BadArgError(fn, var, typ, locs[var])
> BadArgError:
> g: argument b must be <class '__main__.Z'>!
> <__main__.A object at 0x00C92F70> of <class '__main__.A'> given.
>
> (One could easily tidy up this output - that's *not* the problem)
>
> I feel it to be cumbersome and ugly, to have to pass the function (method)
> and
> the locals() dictionary to every call of checkargs.
>
> I'd very much prefer a usage of checkargs similar to:
>
> class A(object):
> def f(self,x,y):
> checkargs(int, str)
> def g(self,a,b,c):
> checkargs((int,float), Z, tuple)
>
> but then chackargs had to get information about its caller (name, locals)
> from
> elsewhere (the callstack?). I don't know if this is possible at all, not to
> say
> how to accomplish it.
>
> Do you have some hints?
> Where could I find code-examples which solve similar problems?
> Would you recommend a different approach?
>
> Regards,
>
> Gregor
>
>
>
>
>
--
Ing. Ewald Ertl HartterGruppe Phone :
+43-3352-33085-558
trinomic Projektmanagement & Informationstechnik GmbH Fax :
+43-3352-33085-600
Wiener Straße 41 mailto:[EMAIL PROTECTED]
A-7400 Oberwart http://www.trinomic.com mailto:[EMAIL PROTECTED]
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