Question

How would I use python to check a list and delete all duplicates? I don’t want to have to specify what the duplicate item is – I want the code to figure out if there are any and remove them if so, keeping only one instance of each. It also must work if there are multiple duplicates in a list.

For example, in my code below, the list lseparatedOrbList has 12 items – one is repeated six times, one is repeated five times, and there is only one instance of one. I want it to change the list so there are only three items – one of each, and in the same order they appeared before. I tried this:

for i in lseparatedOrbList:
   for j in lseparatedOrblist:
        if lseparatedOrbList[i] == lseparatedOrbList[j]:
            lseparatedOrbList.remove(lseparatedOrbList[j])

But I get the error:

Traceback (most recent call last):
  File "qchemOutputSearch.py", line 123, in <module>
    for j in lseparatedOrblist:
NameError: name 'lseparatedOrblist' is not defined

I’m guessing because it’s because I’m trying to loop through lseparatedOrbList while I loop through it, but I can’t think of another way to do it.

Answer 1

Just make a new list to populate, if the item for your list is not yet in the new list input it, else just move on to the next item in your original list.

for i in mylist:
  if i not in newlist:
    newlist.append(i)