Jonathan Jonathan - 8 months ago 65
Python Question

Check for presence of a sublist in Python

I want to write a function that determines if a sublist exists in a larger list.

list1 = [1,0,1,1,1,0,0]
list2 = [1,0,1,0,1,0,1]

#Should return true
sublistExists(list1, [1,1,1])

#Should return false
sublistExists(list2, [1,1,1])

Is there a Python function that can do this?


If you are sure that your inputs will only contain the single digits 0 and 1 then you can convert to strings:

def sublistExists(list1, list2):
    return ''.join(map(str, list2)) in ''.join(map(str, list1))

This creates two strings so it is not the most efficient solution but since it takes advantage of the optimized string searching algorithm in Python it's probably good enough for most purposes.

If efficiency is very important you can look at the Boyer-Moore string searching algorithm, adapted to work on lists.

A naive search has O(n*m) worst case but can be suitable if you cannot use the converting to string trick and you don't need to worry about performance.