Python element-wise tuple operations like sum

Question

Is there anyway to get tuple operations in Python to work like this:

>>> a = (1,2,3)
>>> b = (3,2,1)
>>> a + b
(4,4,4)

instead of:

>>> a = (1,2,3)
>>> b = (3,2,1)
>>> a + b
(1,2,3,3,2,1)

I know it works like that because the __add__ and __mul__ methods are defined to work like that. So the only way would be to redefine them?

Answer 1

import operator
tuple(map(operator.add, a, b))

Answer 2

Using all built-ins..

tuple(map(sum, zip(a, b)))

Answer 3

This solution doesn't require an import:

tuple(map(lambda x, y: x + y, tuple1, tuple2))

Answer 4

Sort of combined the first two answers, with a tweak to ironfroggy's code so that it returns a tuple:

import operator

class stuple(tuple):
    def __add__(self, other):
        return self.__class__(map(operator.add, self, other))
        # obviously leaving out checking lengths

>>> a = stuple([1,2,3])
>>> b = stuple([3,2,1])
>>> a + b
(4, 4, 4)

Note: using self.__class__ instead of stuple to ease subclassing.

Answer 5

from numpy import array

a = array( [1,2,3] )
b = array( [3,2,1] )

print a + b

gives array([4,4,4]).

See http://www.scipy.org/Tentative_NumPy_Tutorial

Answer 6

Generator comprehension could be used instead of map. Built-in map function is not obsolete but it's less readable for most people than list/generator/dict comprehension, so I'd recommend not to use map function in general.

tuple(p+q for p, q in zip(a, b))

Answer 7

simple solution without class definition that returns tuple

import operator
tuple(map(operator.add,a,b))

Answer 8

All generator solution. Not sure on performance (itertools is fast, though)

import itertools
tuple(x+y for x, y in itertools.izip(a,b))

Answer 9

even simpler and without using map, you can do that

>>> tuple(sum(i) for i in zip((1, 2, 3), (3, 2, 1)))
(4, 4, 4)

Answer 10

Yes. But you can't redefine built-in types. You have to subclass them:

class MyTuple(tuple):
    def __add__(self, other):
         if len(self) != len(other):
             raise ValueError("tuple lengths don't match")
         return MyTuple(x + y for (x, y) in zip(self, other))

Answer 11

I currently subclass the "tuple" class to overload +,- and *. I find it makes the code beautiful and writing the code easier.

class tupleN(tuple):
    def __add__(self, other):
        if len(self) != len(other):
             return NotImplemented
        else:
             return tupleN(x+y for x,y in zip(self,other))
    def __sub__(self, other):
        if len(self) != len(other):
             return NotImplemented
        else:
             return tupleN(x-y for x,y in zip(self,other))
    def __mul__(self, other):
        if len(self) != len(other):
             return NotImplemented
        else:
             return tupleN(x*y for x,y in zip(self,other))


t1 = tupleN((1,3,3))
t2 = tupleN((1,3,4))
print(t1 + t2, t1 - t2, t1 * t2, t1 + t1 - t1 - t1)
(2, 6, 7) (0, 0, -1) (1, 9, 12) (0, 0, 0)

Answer 12

Here is another handy solution if you are already using numpy. It is compact and the addition operation can be replaced by any numpy expression.

import numpy as np
tuple(np.array(a) + b)

Answer 13

In case someone need to average a list of tuples:

import operator 
from functools import reduce
tuple(reduce(lambda x, y: tuple(map(operator.add, x, y)),list_of_tuples))