Check if an element in a list is present in multiple lists in python

Question

I have to check if an element in list is present in multiple list.

Example:

cornerCase = [-1, 4]
top = [1, 2]
bottom = [2, 3]
left = [-1, 2]
right = [3,1]

In this case I have to check if -1 or 4 is present in any of the elements in top, bottom, left or right lists. Looking for a solution in more pythonic way.

My attempts:

1. 
    check = [i for i in cornerCase if i in top or bottom or left or right]

Didn't work. Realized after or it looks for other expression.

2.
    check = [i for i in cornerCase if i in (top, bottom, left, right)]

Damn! Didn't work again. Anyone please explain why ?

3.
    check = [i for i in cornerCase if i in [top, bottom, left, right]]

Obviously didn't work because checking a element in a list of lists.

I check if check != [] then -1 or 4 was found in those lists.

Any good pythonic way to achieve this ? Not looking for a solution with multiple for loops and individual if statements for all the lists.

frunkad · Accepted Answer · 2015-10-11 18:53:53Z

9

Though It may not be a very nice solution but it works simple and well,

check = [i for i in cornerCase if i in top + bottom + left + right]

answered Oct 11, 2015 at 18:53

frunkad

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1 Comment

Yogeesh Seralathan Over a year ago

Well, it works. Nice little hack by joining all the lists.

Yogeesh Seralathan · Accepted Answer · 2015-10-12 23:17:08Z

2

As its just wanted to just check if -1 or 4 is present. any builtin function in python comes handy and returns True or False. So there won't be any need of if check != []:

>>> any(item in l for item in cornerCase for l in (top, bottom, left, right))
True

And Drashan's solution also works fine.

answered Oct 12, 2015 at 23:17

Yogeesh Seralathan

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Comments

Alessandro · Accepted Answer · 2015-10-11 19:18:46Z

0

Easy way: for c in cornerCase: if c in top or i in left or i in bottom or i in right: return true else return false

OR: List=[top,left,right,bottom] for c in cornerCase: if c in List return true else return false

answered Oct 11, 2015 at 19:18

Alessandro

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Comments

Arthur Camara · Accepted Answer · 2015-10-11 20:29:26Z

0

The easiest way (and maybe not way too pythonic) is to simple iterate over cornerCase and check if any of these are in any of the other lists:

def check(cornerCase, top, left, bottom, right):
  for i in cornerCase:
    if i in top or i in left or i in bottom or i in right:
      return true
  return false

edited Oct 11, 2015 at 20:29

answered Oct 11, 2015 at 19:05

Arthur Camara

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1 Comment

Yogeesh Seralathan Over a year ago

Works, but I would better do this : check = [i for i in cornerCase if i in top or i in bottom or i in left or i in right]

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