How to find out if a given number is in a list of lists of numbers?

Question

I want to make a function that finds out if a given number is in a list of lists of numbers. How do I fix the following code so that it works for a list consisting of lists?

lst = [[1, 2], [3, 4],[5, 6, 7]]
num = 9

def in_list_of_list(lst: list) -> bool:

    i = 0

    while i < len(lst) and lst[i] != num:
        i = i + 1
    return i < len(lst)
    
print(in_list_of_list(lst))

*How do I fix the following code* what errors/problems are you getting/facing? — Abhyuday Vaish, Apr 30 '22 at 14:32
Does this answer your question? [Check if an item is in a nested list](https://stackoverflow.com/questions/40514139/check-if-an-item-is-in-a-nested-list) — Abhyuday Vaish, Apr 30 '22 at 14:40

score 0 · Answer 1 · answered Apr 30 '22 at 14:37

You can flatten the list first, and then check easily in the flat one:

lst = [[1, 2], [3, 4], [5, 6, 7]]

num = 9


def in_list_of_list(lst: list) -> bool:
    flat_list = [item for sublist in lst for item in sublist]
    return num in flat_list


print(in_list_of_list(lst))

codester_09 · Answer 2 · 2022-04-30T16:57:10.427

0

lst = [[1, 2], [3, 4],[5, 6, 7]]
num = 9

def in_list_of_list(lst: list) -> bool:
    new_lst = []
    for a in lst:
        new_lst.extend(a) # add element from the inner list to new_list.
    return num in new_lst  # return True if the num inside the list else False.

print(in_list_of_list(lst))

edited Apr 30 '22 at 16:57

answered Apr 30 '22 at 14:48

codester_09

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Code-only answers are discouraged here on Stack Overflow. Please [edit] your answer to include supporting information, like how/why it works, so that other users can make more use of your answer. – Sylvester Kruin Apr 30 '22 at 16:53

score 0 · Answer 3 · answered Apr 30 '22 at 15:11

you ask if the item is inside any of the elements of the list

def in_list_of_list(lst: list, item:object) -> bool:
    for sublist in lst:
        if item in sublist:
            return True
    return False

and a quick test

>>> lst = [[1, 2], [3, 4],[5, 6, 7]]
>>> in_list_of_list(lst, 9)
False
>>> in_list_of_list(lst, 7)
True
>>>

How to find out if a given number is in a list of lists of numbers?

3 Answers3