How to test if a list contains another list?

python list contains list-comparison
None picture None · Oct 2, 2010 · Viewed 98.8k times · Source

How can I test if a list contains another list (ie. it's a contiguous subsequence). Say there was a function called contains:

contains([1,2], [-1, 0, 1, 2]) # Returns [2, 3] (contains returns [start, end])
contains([1,3], [-1, 0, 1, 2]) # Returns False
contains([1, 2], [[1, 2], 3]) # Returns False
contains([[1, 2]], [[1, 2], 3]) # Returns [0, 0]

Edit:

contains([2, 1], [-1, 0, 1, 2]) # Returns False
contains([-1, 1, 2], [-1, 0, 1, 2]) # Returns False
contains([0, 1, 2], [-1, 0, 1, 2]) # Returns [1, 3]

Answer

Thomas O picture Thomas O · Oct 2, 2010

If all items are unique, you can use sets.

>>> items = set([-1, 0, 1, 2])
>>> set([1, 2]).issubset(items)
True
>>> set([1, 3]).issubset(items)
False

Related questions

Is there a short contains function for lists?

I see people are using any to gather another list to see if an item exists in a list, but is there a quick way to just do?: if list.contains(myItem): # do something

Read More
Finding the index of an item in a list

Given a list ["foo", "bar", "baz"] and an item in the list "bar", how do I get its index (1) in Python?

Read More
How do I get the number of elements in a list?

Consider the following: items = [] items.append("apple") items.append("orange") items.append("banana") # FAKE METHOD: items.amount() # Should return 3 How do I get the number of elements in the list items?

Read More