python class instance method call from another class instance

Question

I have a quick question regarding python classes. The following is the setup: I have one class as the "mastermind" class which contains various instances of other classes. Now these classes need to call a method of that other class, but I don't know how to do that. For example:

class mastermind(object):
 def __init__(self):
 self.hand = hand()
 def iNeedToCallThisMethod(self, funzies):
 print funzies
class hand(object):
 def __init(self):
 pass #here should be a call to the mastermind instance's method
example = mastermind()

Hope you guys can help me with that, my brain is steaming! Thanks a lot!

Answer 1

If you want to call mastermind's method, you need to have a reference to it.

For example

class mastermind(object):
 def __init__(self):
 self.hand = hand(self)
 def iNeedToCallThisMethod(self, funzies):
 print funzies
class hand(object):
 def __init__(self, mastermind)
 mastermind.iNeedToCallThisMethod('funzies')

• yggdra: Thanks! That worked fine! But doesn't it take a lot more resources if I save the Mastermind instance into the other instance? Or is it really just a reference?
• Peter Uhnak: In the example I've given you are not even saving the instance - the method is called on a provided parameter. But even if you did save it, it is just a reference, so there is no reason to worry about it unless you have hundreds of thousands of hands.

Answer 2

If you need to call iNeedToCallThisMethod from the __init__ of hand, you should probably put the method in that class.

However, what you want to do can be achieved using a classmethod:

class mastermind(object):
 def __init__(self):
 self.hand = hand()
 @classmethod
 def iNeedToCallThisMethod(cls, funzies):
 print funzies
class hand(object):
 def __init__(self):
 mastermind.iNeedToCallThisMethod('funzies')
example = mastermind()

Answer 3

Both object need a reference to one another, try passing the instance to the constructor.

class Mastermind(object):
 def __init__(self):
 self.hand = Hand(self)
 def test_funct(self, arg):
 print arg
class Hand(object):
 def __init(self, mastermind):
 self.mastermind = mastermind
 self.mastermind.test_funct()

Answer 4

class hand(object):
 def __init(self, other_class):
 #here should be a call to the mastermind instance's method
 other_class.iNeedToCallThisMethod()
m_m = mastermind()
example = hand(m_m) # passes mastermind to new instance of hand

I'd just pass the object like above

• Malik Brahimi: You've got this all wrong, you need a reference between both object.
• JGerulskis: Can you elaborate I believe what I posted is correct @MalikBrahimi
• Alejandro: iNeedToCallThisMethod is an instance method, so cannot therefore be called directly using the mastermind class, as you posted. mastermind.iNeedToCallThisMethod() would only be valid for class methods and static methods.
• JGerulskis: I believe you have mistaken that the mastermind was a call to the class mastermind but it was actually a call to a parameter being passed to the class. I should've made that clearer but the code works fine. I've changed mastermind to other_class
• Alejandro: YES! So sorry, didn't realize that at all. The variable name threw me off