How to delete elements in a list using delete order?

Ding medicine

I have a list like this lst = [1,3,5]and a main list like thislost =['the' , 'cat' , 'thinks' , 'you' , 'are' , 'crazy' ]

I want to remove elements in the second list based on the index in the first list. This means I have to remove 'cat', 'you' and 'crazy'.

The problem is if I use:

lost.remove(lost[1])
lost.remove(lost[3])
lost.remove(lost[5])

The first problem is that it won't work! Because when we remove the first element, the length of the list ( named lost ) decreases, so that we will remove the wrong element.

The second problem is that the list named ( lst ) is not always [1,3,5]. It changes length and elements.

How can I fix this problem?

gorisanson

As @np8 commented , you can remove elements in descending index order like this :

lst = [1, 3, 5]
lost = ['the', 'cat', 'thinks', 'you', 'are', 'crazy']

for index in reversed(lst):  # descending index order
    del lost[index]

print(lost)

which prints

['the', 'thinks', 'are']

UPDATE (Thanks to @wwii for the comment )

If the given lstis not sorted in ascending order, you can do:

lst = [3, 1, 5]
lost = ['the', 'cat', 'thinks', 'you', 'are', 'crazy']

for index in sorted(lst, reverse=True):  # descending index order
    del lost[index]

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