CODEWITHSUNDEEP
python
eun ason
eun ason

Reputation: 29

How do I find a previous element in a list?

n = 2
list1 = [1,4,6,2,8,9,90]

How would I go about finding the number prior to the number n stored above in list1 and store it in the variable list1_result?

Upvotes: 2

Views: 7541

Answers (4)

nazia
nazia

Reputation: 75

You can write a function which will scan through your list and return the desired number if found a match with n Try this:

def find_previous(List1, n):
    for i in range(len(List1)):
        if List1[i] == n and i > 0:
            return List1[i-1]
    return None

Upvotes: 0

etemple1
etemple1

Reputation: 1788

You'll want to find the index of n in the list then subtract 1 to get the position of the element before it.

n = 2
List1 = [1,4,6,2,8,9,90]
prev_elem = List1[List1.index(n) - 1]

Upvotes: 0

Ajax1234
Ajax1234

Reputation: 71451

You can find the index of the number in the list and then use that to find the previous element:

lst = [1,4,6,2,8,9,90]
the_index = lst.index(n)
lst2 = lst[the_index-1]

Now, you have the new list stored in lst2

Upvotes: 0

Rafael
Rafael

Reputation: 3196

This should work:

List1 = [1,4,6,2,8,9,90]
n = 2
ind = List1.index(n)
list1_result = List1[ind-1] # is 6

Upvotes: 3

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