Adding Values From Tuples of Same Length

Question

In a graphical program I\'m writing using pygame I use a tuple representing a coordinate like this: (50, 50).

Sometimes, I call a function which returns another tupl

Answer 1

To get your "+" and "+=" behaviour you can define your own class and implement the __add__() method. The following is an incomplete sample:

# T.py
class T(object):
    def __init__(self, *args):
        self._t = args
    def __add__(self, other):
        return T(*([sum(x) for x in zip(self._t, other._t)]))
    def __str__(self):
        return str(self._t)
    def __repr__(self):
        return repr(self._t)

>>> from T import T
>>> a = T(50, 50)
>>> b = T(3, -5)
>>> a
(50, 50)
>>> b
(3, -5)
>>> a+b
(53, 45)
>>> a+=b
>>> a
(53, 45)
>>> a = T(50, 50, 50)
>>> b = T(10, -10, 10)
>>> a+b
(60, 40, 60)
>>> a+b+b
(70, 30, 70)

EDIT: I've found a better way...

Define class T as a subclass of tuple and override the __new__ and __add__ methods. This provides the same interface as class tuple (but with different behaviour for __add__), so instances of class T can be passed to anything that expects a tuple.

class T(tuple):
    def __new__(cls, *args):
        return tuple.__new__(cls, args)
    def __add__(self, other):
        return T(*([sum(x) for x in zip(self, other)]))
    def __sub__(self, other):
        return self.__add__(-i for i in other)

>>> a = T(50, 50)
>>> b = T(3, -5)
>>> a
(50, 50)
>>> b
(3, -5)
>>> a+b
(53, 45)
>>> a+=b
>>> a
(53, 45)
>>> a = T(50, 50, 50)
>>> b = T(10, -10, 10)
>>> a+b
(60, 40, 60)
>>> a+b+b
(70, 30, 70)
>>> 
>>> c = a + b
>>> c[0]
60
>>> c[-1]
60
>>> for x in c:
...     print x
... 
60
40
60