8kyu_Find the first non-consecutive number.py

'''
Find the first non-consecutive number
https://www.codewars.com/kata/58f8a3a27a5c28d92e000144/train/python

Your task is to find the first element of an array that is not consecutive.
By not consecutive we mean not exactly 1 larger than the previous element of the array.
E.g. If we have an array [1,2,3,4,6,7,8] then 1 then 2 then 3 then 4 are all consecutive but 6 is not, so that's the first non-consecutive number.

If the whole array is consecutive then return null2.
The array will always have at least 2 elements1 and all elements will be numbers.
The numbers will also all be unique and in ascending order. The numbers could be positive or negative and the first non-consecutive could be either too!
If you like this Kata, maybe try this one next: https://www.codewars.com/kata/represent-array-of-numbers-as-ranges

1 Can you write a solution that will return null2 for both [] and [ x ] though?
(This is an empty array and one with a single number and is not tested for, but you can write your own example test. )
'''

def first_non_consecutive(arr):
    mmin = min(arr)
    mmax = max(arr)
    wrk_ = set(arr)
    def_ = set(list(range(mmin,mmax+1)))
    rznl = list(def_ - wrk_)

    if len(rznl) == 0: return None
    rznl.sort()
    if (rznl[0]+1) in arr:
        return rznl[0]+1
    else:
        return None

# Jne of the best of Codewars
# def first_non_consecutive(arr):
#     for i in range(1, len(arr)):
#         if arr[i] - arr[i-1] > 1:
#             return arr[i]


print(first_non_consecutive([1,2,3,4,5,6,7,8]))