I guess it would be easy for me to explain the question with an examply Suppose I want to write my own vector class. And in that class let say i want to define a method to add 2 vectors something like:
class vector:
.....
def add(self,other):
----some code
so basically what this will do is.. if a vector is vec then
vec.add(othervec)
will do the addition.. but how do i do this.. its like inherting your own class..datatype ? Thanks
If you want to add two classes, I'd look at the __add__ function, which allows you to do normal addition (and not call .add()):
a + b
As for your question, I'm not exactly sure about what you're asking. I wrote my Vector() class like this:
class Vector:
def __init__(self, x = 0, y = 0, z = 0):
self.x = x
self.y = y
self.z = z
def __add__(self, other):
return Vector(self.x + other.x, self.y + other.y, self.z + other.z)
In Python, you should use duck typing, i.e. not worry about the type at all:
class Vector(object):
def __init__(self, x, y):
self.x = x
self.y = y
def add(self, othervec):
return Vector(self.x + othervec.x, self.y + othervec.y)
If you want, you can make add modify the Vector object instead of returning a new one. However, that makes your class mutable and therefore harder to deal with:
def add_mutable(self, othervec):
self.x += othervec.x
self.y += othervec.y
sure, you can do exactly as you said, suppose you are wanting to add / change functionality of list
class Vector(list):
def add(self, v):
list.extend(self, v)
and you can use it like this:
> v = Vector([1,2,3])
> v.add([4,5,6])
> print v
> [1, 2, 3, 4, 5, 6]
