calling a function from class in python - different way
class MathsOperations:
def __init__ (self, x, y):
self.a = x
self.b = y
def testAddition (self):
return (self.a + self.b)
def testMultiplication (self):
return (self.a * self.b)
then
temp = MathsOperations()
print(temp.testAddition())
you have to use self as the first parameters of a method
in the second case you should use
class MathOperations:
def testAddition (self,x, y):
return x + y
def testMultiplication (self,a, b):
return a * b
and in your code you could do the following
tmp = MathOperations()
print tmp.testAddition(2,3)
if you use the class without instantiating a variable first
print MathOperation.testAddtion(2,3)
it gives you an error "TypeError: unbound method"
if you want to do that you will need the @staticmethod
decorator
For example:
class MathsOperations:
@staticmethod
def testAddition (x, y):
return x + y
@staticmethod
def testMultiplication (a, b):
return a * b
then in your code you could use
print MathsOperations.testAddition(2,3)
disclaimer: this is not a just to the point answer, it's more like a piece of advice, even if the answer can be found on the references
IMHO: object oriented programming in Python sucks quite a lot.
The method dispatching is not very straightforward, you need to know about bound/unbound instance/class (and static!) methods; you can have multiple inheritance and need to deal with legacy and new style classes (yours was old style) and know how the MRO works, properties...
In brief: too complex, with lots of things happening under the hood. Let me even say, it is unpythonic, as there are many different ways to achieve the same things.
My advice: use OOP only when it's really useful. Usually this means writing classes that implement well known protocols and integrate seamlessly with the rest of the system. Do not create lots of classes just for the sake of writing object oriented code.
Take a good read to this pages:
- http://docs.python.org/reference/datamodel.html
- http://docs.python.org/tutorial/classes.html
you'll find them quite useful.
If you really want to learn OOP, I'd suggest starting with a more conventional language, like Java. It's not half as fun as Python, but it's more predictable.