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?
Solution
import operator
tuple(map(operator.add, a, b))
OTHER TIPS
Using all built-ins..
tuple(map(sum, zip(a, b)))
This solution doesn't require an import:
tuple(map(lambda x, y: x + y, tuple1, tuple2))
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.
from numpy import *
a = array( [1,2,3] )
b = array( [3,2,1] )
print a + b
gives array([4,4,4])
.
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))
simple solution without class definition that returns tuple
import operator
tuple(map(operator.add,a,b))
All generator solution. Not sure on performance (itertools is fast, though)
import itertools
tuple(x+y for x, y in itertools.izip(a,b))
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))
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)
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)
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))