Increase the last element in a tuple

Question

I want to implement a function that takes a tuple of ints and increases the last element by 1:

inc((0,0,0,1))==(0,0,0,2)
inc((1,2,3))==(1,2,4)

This is what I came up with:

def inc(t):
   l=list(t)
   l[-1]+=1
   return tuple(l)

Can this be done in a more compact way (and maybe without the conversion to list) ?

I don't know why this is downvoted but do you have to use tuples for this ? They are, you know, immutable. — percusse, Nov 20 '16 at 21:46
@percusse, I have a feeling this could be done with a one liner — Uri Goren, Nov 20 '16 at 21:48
@RomanPerekhrest I am not modifying elements, I am creating a copy, there is a reason why I am using a tuple — Uri Goren, Nov 20 '16 at 21:50
Without the *mutable* lingo, you cannot modify a tuple value without creating a new one. You can instead use lists. — percusse, Nov 20 '16 at 21:50

jez · Accepted Answer · 2016-11-20T22:01:47.177

3

A tuple cannot be modified in-place. If it's very important to use the tuple type rather than a mutable sequence, then the following code will do what you want without converting:

def inc(t):
    return t[:-1] + (t[-1] + 1,)

Note that it has to create three new tuples in order to accomplish this. I don't know that the overhead involved in that is going to be any smaller than the overhead in converting to & from list.

edited Nov 20 '16 at 22:01

answered Nov 20 '16 at 21:47

jez

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Nicely done, avoiding lists, and good commentary on your code's strengths and weaknesses. – Rory Daulton Nov 20 '16 at 22:04

Increase the last element in a tuple

1 Answers1