Removing multiple item from a list for each criteria not being fulfilled

Question

I need to build a function that takes a list and removes every item that doesn't meet all the criteria's I've specified.

The structure is the following :

def function(my_list):

    for element in my_list:
        if not criteria_1:
            my_list.remove(element)

        else:
            if not criteria_2:
                my_list.remove(element)

    return my_list

The issue is that the list I get as a result contains elements that don't match the criteria's
The expected output is a list that contains only elements that match all the criteria's.

The problem is that you are iterating and deleting at the same time, — Dani Mesejo, Nov 03 '21 at 09:52
which means you should append the good elements to a new `list`, or iterate over the `list` from back to front — Mahrkeenerh, Nov 03 '21 at 09:53
What do you mean ? What would be the correct structure of the function instead ? — Madal, Nov 03 '21 at 09:54

score 0 · Accepted Answer · answered Nov 03 '21 at 09:55

0

You can make a one big if - it is more readable (i think at least)
You are deleting and iterating simultaneously which is incorrect - you need to create temporary list

This code should work:

def function(my_list):
    tmp = list(my_list)
    
    for element in my_list:
        if not (criteria1 and criteria2 and criteria3):
            tmp.remove(element)

    return tmp

answered Nov 03 '21 at 09:55

Jakub Szlaur

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I wouldn't create a copy of the list and then remove data from it. I would create a new list with just the elements I need. Then the whole body of the function boils down to `return [element for element in my_list if criteria1 and criteria2 and criteria3]`. – Matthias Nov 03 '21 at 10:28
Yea you're right. Didn't think of it when I was creating the answer :) – Jakub Szlaur Nov 03 '21 at 10:31

Removing multiple item from a list for each criteria not being fulfilled

1 Answers1