How do i instantiate a class_name passed via cmd line

Gregory Ewing greg.ewing at canterbury.ac.nz
Sun Feb 14 00:41:54 EST 2016


Veek. M wrote:
> I'm writing a price parser. I need to do the equivalent of perl's
> $$var to instantiate a class where $car is the class_name.
> 
> I'm passing 'Ebay' or 'Newegg' or 'Amazon' via cmd-line. I have a module 
> named ebay.py and a class called Ebay (price parser). I do something 
> like:
> 
> \> main.py ebay motherboard
> 
> and this does: 
>  module = __import__(module_name)
> but now i need to instantiate the class - right now I do:
>  instance = module.Ebay(module_name, product)
> 
> how do i replace the 'Ebay' bit with a variable so that I can load any 
> class via cmd line.
> 
> class Load(object):
>     def __init__(self, module_name, product):
>         try:
>             module = __import__(module_name)
>             instance = module.Ebay(module_name, product)
>         except ImportError:
>             print("Can't find module %s" % module_name)
> 

Something like this should do it:

   instance = getattr(module, class_name)(module_name, product)

If the class name is always the same as the module name with the
first letter capitalized, you could use

   instance = getattr(module, module_name.capitalize())(module_name, product)

-- 
Greg


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