list index out of range: python -

i have list has these elements(list consists str(elements)):

['-0', '1', '2', '3', '4', '5', '6', '7', '8', '9', '10', '11', '12', '13', '14', '15'] 

and want process have output this

['-0', '1#', '15#'] 

if element -x want leave there take last 2 elements , if gap 1 remove element before last element. here code:

            k in range(len(l1)):                 if "-" in (l1[-k] or l1[-k-1]):                     print("debuggggg")                     pass                 elif(int(l1[-k]) - int(l1[-k-1])== 1 , int(l1[-k]) - int(l1[-k-2])== 2) :                     a= l1[-2]                     print(a)                     l1.remove(a)                     #print("debug 2")                 elif(int(l1[-k]) - int(l1[-k-1])== 1):                     a= l1[-2]                     l1.remove(a)                     l1[-2] = l1[-2] +"#"                     l1[-1] = l1[-1] +"#"                     print("3")                 #elif(type(l1[-2]) str):                     #pass 

problem here :

 debuggggg     14     13     12     11     10     9     8 

the last 2 elements not include char "-" seems do. furthermore after 8 loop script crashes:

 elif(int(l1[-k]) - int(l1[-k-1])== 1 , int(l1[-k]) - int(l1[-k-2])== 2) : indexerror: list index out of range 

but not out range of list. problem?

your second question

but not out range of list. problem?

it out of range error.

l1[-len(l1)-1] 

raises error. doing in code.

for k in range(len(l1)):     ...     elif(int(l1[-k]) - int(l1[-k-1])== 1 , int(l1[-k]) - int(l1[-k-2])== 2) :#<--here(l1[-k-2])