Find/extract a sequence of integers within a list in python

Question

I want to find a sequence of n consecutive integers within a sorted list and return that sequence. This is the best I can figure out (for n = 4), and it doesn't allow the user to specify an n.

my_list = [2,3,4,5,7,9]
for i in range(len(my_list)):
    if my_list[i+1] == my_list[i]+1 and my_list[i+2] == my_list[i]+2 and my_list[i+3] == my_list[i]+3:
        my_sequence = list(range(my_list[i],my_list[i]+4))

my_sequence = [2,3,4,5]

I just realized this code doesn't work and returns an "index out of range" error, so I'll have to mess with the range of the for loop.

Answer 1

Here's a straight-forward solution. It's not as efficient as it might be, but it will be fine unless you have very long lists:

myarray = [2,5,1,7,3,8,1,2,3,4,5,7,4,9,1,2,3,5]
for idx, a in enumerate(myarray):
    if myarray[idx:idx+4] == [a,a+1,a+2,a+3]:
        print([a, a+1,a+2,a+3])
        break

Answer 2

Create a nested master result list, then go through my_sorted_list and add each item to either the last list in the master (if discontinuous) or to a new list in the master (if continuous):

>>> my_sorted_list = [0,2,5,7,8,9]
>>> my_sequences = []
>>> for idx,item in enumerate(my_sorted_list):
...     if not idx or item-1 != my_sequences[-1][-1]:
...         my_sequences.append([item])
...     else:
...         my_sequences[-1].append(item)
...
>>> max(my_sequences, key=len)
[7, 8, 9]