Get next number from a list of numbers

Question

I have a list of numbers(let's say list_num = []) from 0 to x. It may not contain all the numbers between 0 and x (ie, skipping say 4 and 7), but I don't know.

I want to get the first missing number from the list or, if none are missing, I want to get the next number after ( something like: len(list_num) <- no +1 because the list starts at 0).

I have tried this and this, but they are both slightly different

How can I do this Python 3? I don't mind using some APIs.

Lack of effort on your part. Show what you've tried and where you are stuck. — JJJ, Oct 28 '17 at 12:08
This can be done using simple `for` loops. Put in some effort? — aaron, Oct 28 '17 at 12:09
Better add explicit examples. That would make it clearer and make it easier for us to test our code. — Stefan Pochmann, Oct 28 '17 at 12:27

score 3 · Accepted Answer · answered Oct 28 '17 at 12:11

3

Get the first item matching the condition. If none, you need x+1

try:
    first_value = next(val for val in range(x) if val not in list_sum)
except StopIteration:
    first_value = x+1

answered Oct 28 '17 at 12:11

blue_note

27,712
9
72
90

1

Thanks. This is simple and short – Sank6 Oct 28 '17 at 12:17

score 1 · Answer 2 · answered Oct 28 '17 at 12:16

You could make it with sets:

>>> lst = set([1,2,3,4,5,9,11,14])
>>> set(range(0, max(lst))).difference(lst)
{0, 6, 7, 8, 10, 12, 13}

or list comprehensions:

>>> lst = set([1,2,3,4,5,9,11,14])
>>> allNumbers = list(range(0, max(lst)))
>>> [x for x in allNumbers if x not in lst]
[0, 6, 7, 8, 10, 12, 13]

Get next number from a list of numbers

2 Answers2