[Tutor] creating objects in a loop

[Alexandre Ratti]

Hello Brad,


At 15:14 02/04/2002 -0500, you wrote:
>From: "Brad Reisfeld" <brad.reisfeld@colostate.edu>
>Date: Tue, 2 Apr 2002 11:33:37 -0700
>Subject: [Tutor] creating objects in a loop

>I was wondering if there is an efficient way to create objects based on
>looping through members of a list or dictionary.
>
>For instance, suppose I have
>
> >>> class Pets:
>...   def __init__(self, name):
>...     self.name = name
>
> >>> petlist = [('cat','fluffy'),('dog','fido'),('gorilla','spike')]

This is a bit off-topic, but you might be interested in using functions as 
class factories:

class Pets:
     def __init__(self, name):
         self.name = name

def factory(theClass, *args):
     "theClass is a class object."
     return theClass(*args)

def factoryFromName(className, *args):
     "className is a string."
     return eval(className)(*args)

def petFactory(arg):
     # This could be extended to accept a list of args
     # and return a list of class instances
     return Pets(arg)

if __name__ == "__main__":
     cat = factory(Pets, "fluffy")
     print cat

     monkey = factoryFromName("Pets", "foo")
     print monkey

     pet = petFactory("bombix")
     print pet

<__main__.Pets instance at 00FBFA7C>
<__main__.Pets instance at 00FBEFDC>
<__main__.Pets instance at 00FBB90C>

Also, if you have a lot of pets to handle, you could use a collection class 
to manage them. Eg.:

class BunchOfPets:

     def __init__(self):
         self.petDict = {}

     def addPet(self, name):
         pet = Pets(name)
         self.petDict[name] = pet

     def getPet(self, name):
         if self.petDict.has_key(name):
             return self.petDict[name]
         else:
             return None

     def getPetCount(self):
         return len(self.petDict)

if __name__ == "__main__":

     bunch = BunchOfPets()
     bunch.addPet("snafu")
     print bunch.getPetCount()
     print bunch.getPet("snafu")

1
<__main__.Pets instance at 018592FC>


Cheers.

Alexandre