Python class instantiation using name

[David Eppstein]

In article <mailman.1040166033.32587.python-list at python.org>,
 Chad Netzer <cnetzer at mail.arc.nasa.gov> wrote:

> On Tuesday 17 December 2002 14:16, holger krekel wrote:
> > Amol P Dharmadhikari wrote:
> >     cls = eval(classname)
> >
> > if the class is defined in the current module.  or
> >
> >     cls = eval(classname, othermodule.__dict__)
> >
> > if the class lives in another module.
> 
> That code will bind to the class objects, but won't create 
> instances of the classes.
> 
> I would amend the above code to be:
> 
>     instance = eval( classname + "()" )
> 
> or if it is in a module called "othermodule":
> 
>     instance = eval( "othermodule." + classname + "()" )
> 
> You could also use string substitution:
> 
>     instance = eval( "othermodule.%s()" % classname )

Why do you need to concatenate the () within the string and evaluate it, 
when it's easier just to do it outside?

newInstance = eval(classname)()
newInstance = eval(classname, othermodule.__dict__)()

-- 
David Eppstein       UC Irvine Dept. of Information & Computer Science
eppstein at ics.uci.edu http://www.ics.uci.edu/~eppstein/