def get_substring(my_string):
   return my_string[i : j]

my_list = ["python", 'is', 'fun', 'to', 'learn']

print("The list is :")
print(my_list)

i, j = 1, 3
print("The value of i and j are :")
print(str(i)+ ',' +str(j))

my_list.sort(key=get_substring)

print("The result is :")
print(my_list)

The list is :
['python', 'is', 'fun', 'to', 'learn']
The value of i and j are :
1,3
The result is :
['learn', 'to', 'is', 'fun', 'python']