Generate dynamic methods in a class

Question

I want to have a class with dynamic methods.

From these arrays:

prefix = ['android','iphone','blackberry'] 
method = ['AddToPush','DelFromPush','GetPushMessages']

I want to create a class like:

class MobileManager(object)
 def __init__(self):
 self.mobileLib = MobileLib()
 def androidAddToPush(self, args):
 self.mobileLib.AddToPush(args, 'android')
 def iphoneAddToPush(self, args):
 self.mobileLib.AddToPush(args, 'iphone') 
 def blackberryAddToPush(self, args):
 self.mobileLib.AddToPush(args, 'blackberry') 
 [...]

How can I have these methods generated/created at runtime?

Answer 1

If your set of prefixes/methods is defined at init time, you can try something like this:

class MobileManager(object):
 def __init__(self):
 for prefix_name in prefix:
 for method_name in method:
 func = lambda self, args: getattr(self.mobileLib, method_name)(args, prefix)
 full_method_name = "%s%s" % (prefix, method_name)
 setattr(self, full_method_name, func)
 ...

If your dynamic methods get more complicated, the lambda will soon be limited, though.

• Rafał Kot: Will it work like this: self.mobileLib.method_name(args, prefix) ?
• Rafał Kot: In Your code You have line: func = lambda self, args: self.mobileLib.AddToPush(args, prefix) 'AddToPush' should be from method array.
• jfs: It won't work: 1. drop self from func() parameters (you bind it to a concrete instance, not a class). 2. all func will use the last value of method_name. You don't want that.
• jfs: setattr(self, prefix+method_name, make_func(getattr(self.mobileLib, method_name), prefix)) should fix it, where make_func = lambda func, prefix: lambda args: func(args, prefix)
• Rafał Kot: This one is working! make_func = lambda func, prefix_name: lambda args: func(args, prefix_name) setattr(self, prefix_name+method_name, make_func(getattr(self.mobileLib, method_name), prefix_name)) Thanks a lot!

Answer 2

Or why not inherate

class MobileManager(object)
 def __init__(self):
 self.mobileLib = MobileLib()
 def AddToPush(self, args, platform=None):
 self.mobileLib.AddToPush(args, platform)
class Android(MobileManager):
 def __init__(self):
 MobileManager.__init__(self)
 def AddToPush(self, args):
 MobileManager.AddToPush(args, platform="android")

Answer 3

Dynamic methods are often the wrong approach leading to confusing code.

Here, I'd do this:

class Mobile(object):
 def add_to_push(self, args):
 ....
 def del_from_push(self, args):
 ...
 def get_push_methods(self, args):
 ...

And in your Manager:

class MobileManager(object):
 def __init__(self):
 self.android = Mobile()
 self.blackberry = Mobile()
 self.iphone = Mobile()

Now, instead of manager.mobileLib.add_to_push(args, 'android'), you would write manager.android.add_to_push(args).

You can even dispatch dynamically if you have a platform variable: getattr(manager, platform).add_to_push(args).

If you want different behaviour for the 3 types of platform you can make subclasses of Mobile (perhaps AndroidMobile, BlackberryMobile and IPhoneMobile).

When a new platform appears (perhaps windows7) it's obvious how to change the code to support it.