How do i instantiate a class_name passed via cmd line

Veek. M vek.m1234 at gmail.com
Sun Feb 14 00:51:08 EST 2016


Gregory Ewing wrote:

> 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)
> 
Ah! i see - clever!

'getattr' returns the class object with class_name=whatever
and we can instantiate now that we have a class object - nice - thanks 
guys - the bell should have rung from Rick's example.


More information about the Python-list mailing list