Python - is it possible to set a variable to an operator?

Question

I'm developing a bunch of functions that have the same basic structure - they take two lists and use a loop to do a particular operation pairwise for the two lists (for example, one will take each element of a list raised to the power represented by the corresponding element in the second list).

Since all of these function differ only by an operator, I was wondering - is it possible to set a variable to an operator? For example, can you do (something similar to):

var = +
var2 = 5 var 7       #var2 is now 12

I know that specifically doesn't work, but is there anything similar that does work similarly?

kindall · Accepted Answer · 2013-10-04 04:57:33Z

7

Yes! You want the operator module, which "exposes Python's intrinsic operators as efficient functions."

import operator

op = operator.add
var = op(5, 7)

As @falsetru points out, a lambda is handy too; the functions in operator are going to be a wee bit faster, though:

from timeit import timeit
print timeit("add(5, 7)", "add = lambda x, y: x+y")    # about 0.176 OMM
print timeit("add(5, 7)", "from operator import add")  # about 0.136 OMM

edited Oct 4, 2013 at 4:57

answered Oct 4, 2013 at 2:00

kindall

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falsetru · Accepted Answer · 2013-10-04 01:59:36Z

2

Try following:

>>> op = lambda a, b: a + b
>>> result = op(5, 7)
>>> result
12

answered Oct 4, 2013 at 1:59

falsetru

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3 Comments

falsetru Over a year ago

@KevinMills, You can use abitrary expression inside the lambda body (lambda a, b: (a+b)*2). But as @kindall mentioned, if you do simply adding, operator.add is more concise and maybe faster.

Kevin Over a year ago

Is this better than simply defining and passing a subfunction?

falsetru Over a year ago

@KevinMills, You have to define a function if you have multiple statements to execute. If there's only one expression, there's no difference. You can check it by import dis; dis.dis(lambda a, b: a + b). ; So it's your preference which one you use. See ideone.com/AHc6JQ

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