finding index[] of odd values in a list of integers?-CodePudding

I am trying to find the index value of some odd integers in a list. The program at its current stage only returns a new list containing only the odd integers.

image of my code

This program returns the values [3, 5, 7]. How would i be able to retrieve the index of these odd values instead? For example, [0, 1, 3, 5] for the list shown above.

I have tried "position = dataItem1.index()". I understand that i would need to input an index value within the index brackets.

CodePudding user response：

you can use also use enumerate : it returns the index of the element and the element (also, in python you can loop directly over the elements of a list, no need of while loops). I also encourage the use of .append() to add an element to a list, this is clearly more efficient than concatenate two lists as you do:

l = [0, 3, 2, 3, 4, 7, 6]

def get_odds_index(l):
    res = []
    for idx, val in enumerate(l):
        if val % 2 != 0:
            res.append(idx)
    return res

get_odds_index(l)

CodePudding user response：

Instead of adding the element on that index in the odd list, just add index Like this

def positionOfOdds(arr):
    odds = []
    length = len(arr)
    
    index = 0
    while index < length:
        data = arr[index]
        if data % 2 != 0:
            odds.append(index)
        index  = 1
    return odds

CodePudding user response：

you already know the index, it is the loop variable

def positionOfOdds(arr):
    odds = []
    length = len(arr)
    
    index = 0
    while index < length:
        data = arr[index]
        if data % 2 != 0:
            odds = odds   [index]
        index  = 1
    return odds

CodePudding user response：

You use an array called odds to store the odd numbers, to get the indexes you can create instead an array to store the indexes of the odd numbers, which I called odds_idxs. It should look something like this:

num_list = [0, 3, 2, 3, 4, 7, 6]
def position_of_odds(num_list):
  odds_idxs = []
  length = len(num_list)
  index = 0
  while index < length:
    if num_list[index] % 2 != 0:
      odds_idxs = odds_idxs   [index]
    index = index   1 
  return odds_idxs