Question

I’m newbie with python. I want to write a class with two keys as indexer. also need to be able to use them inside of class like this:

a = Cartesian(-10,-10,10,10) # Cartesian is the name of my class
a[-5][-1]=10

and in the Cartesian class:

def fill(self,value):
   self[x][y] = x*y-value

I try with

def __getitem__(self,x,y):
  return self.data[x-self.dx][y-self.dy]

but doesn’t work.

Answer 1

If you just need a lightweight application, you can have __getitem__ accept a tuple:

def __getitem__(self, c):
  x, y = c
  return self.data[x-self.dx][y-self.dy]

def __setitem__(self, c, v):
  x, y = c
  self.data[x-self.dx][y-self.dy] = v

and use like this:

a[-5,-1] = 10

However, if you are doing a lot of numeric computation or this is integral to your application, consider using Numpy and just represent this coordinate as a vector: Link