python sum a value to all the elements in a list

Question

I have a list of int and I'd like to sum a value to all of them. The easy way of doing this is:

[x+y for x in my_list]

Is there a more efficient/pythonic way of doing this?

Possible duplicate of [Sum a list of numbers in Python](https://stackoverflow.com/questions/4362586/sum-a-list-of-numbers-in-python) — Dragin, Jun 15 '18 at 13:23
No, I don't think there is. Unless you use an external dependency like numpy: `list(np.array(x) + y)`. That's definitely not more efficient though. — Mad Physicist, Jun 15 '18 at 13:23
Not really a duplicate, OP is asking if there is a more efficient way, not how to do it. — Attersson, Jun 15 '18 at 13:25
@Attersson. I feel like the "how" is implied, but that's definitely up for interpretation. — Mad Physicist, Jun 15 '18 at 13:34
Yes that was addressed at Dragin, since the additional part reframes the question as different than the assumed duplicate — Attersson, Jun 15 '18 at 13:36

Attersson · Answer 1 · 2018-06-15T13:41:34.403

1

No, the list comprehension is, to date, the fastest.

As proved here map performs worse for all except few cases, in which map is only microscopically better.

It however depends on the context. For example if you were running this on a Spark RDD a lambda would allow parallelization.

Also a generator expression, if you don't need a new list, would save memory.

edited Jun 15 '18 at 13:41

answered Jun 15 '18 at 13:23

Attersson

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score 1 · Accepted Answer · answered Jun 15 '18 at 13:33

I think the way you have it is about as Pythonic as you can get working with lists. Any other option I can think of sacrifices either efficiency or legibility. You could do something like

list(map(y.__add__, my_list))

OR

list(map(partial(operator.add, y), my_list))

If you use an external dependency like numpy:

list(np.array(my_list) + y)

That's definitely not more efficient on its own though. It would only make sense if you wanted np.array(my_list) anyway, and didn't convert back to list.

python sum a value to all the elements in a list

2 Answers2