[FIXED] Easier way to check if an item from one list of tuples doesn't exist in another list of tuples in python

Issue

I have two lists of tuples, say,

list1 = [('item1',),('item2',),('item3',), ('item4',)] # Contains just one item per tuple
list2 = [('item1', 'd',),('item2', 'a',),('item3', 'f',)] # Contains multiple items per tuple

Expected output: 'item4' # Item that doesn't exist in list2

As shown in above example I want to check which item in tuples in list 1 does not exist in first index of tuples in list 2. What is the easiest way to do this without running two for loops?

Solution

Assuming your tuple structure is exactly as shown above, this would work:

tuple(set(x[0] for x in list1) - set(x[0] for x in list2))

or per @don't talk just code, better as set comprehensions:

tuple({x[0] for x in list1} - {x[0] for x in list2})

result:

('item4',)

Answered By - sj95126