Removing Duplicate Numbers in a list with a twist

Question

I have looked around and found the

 if numbers.count(x) >= 2: 
    numbers.remove(x) 
 print(numbers)

but I don't want to use that. I think lazy-ier way is to go like this:

numbers = [1, 2, 3, 4, 5, 5, 6, 7, 8, 9, 2, 5, 12]
numbers.sort()
print(numbers)
duplicate = 0
for each_item in numbers:
  if duplicate == each_item:
    numbers.remove(each_item)
  else:
    duplicate += 1
print(numbers)

I, first, sort the list then print it for manual comparison. I add a variable called duplicate and set it to 0. I go thru the loop for each number in the list numbers. If I find the duplicate's value same as a number in the list, I remove it and go thru the loop, else I increase the value by 1 and print the list.

The problem is if there are more than 2 duplicates in the list it doesn't work. Which I don't understand why. I run the code in my head and it should work "flawlessly"?

Thank you for your time sensei's

Current output is;

[1, 2, 2, 3, 4, 5, 5, 5, 6, 7, 8, 9, 12]
[1, 2, 3, 4, 5, 5, 6, 7, 8, 9, 12]

or maybe `sorted(set(numbers))` - i forgot how set auto-sorts numbers again (I remember there was a post explaining that somewhere) — rv.kvetch, Aug 01 '22 at 18:08
Does this answer your question? [Removing duplicates in lists](https://stackoverflow.com/questions/7961363/removing-duplicates-in-lists) — Will.Evo, Aug 01 '22 at 18:13

score 2 · Answer 1 · answered Aug 01 '22 at 18:07

2

Use a set to make things easy:

numbers = [1, 2, 3, 4, 5, 5, 6, 7, 8, 9, 2, 5, 12]
s = set(numbers)
print(list(s))

[1, 2, 3, 4, 5, 6, 7, 8, 9, 12]

answered Aug 01 '22 at 18:07

NYC Coder

7,424
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Well, it works but I wanted to find the problem with my logic. Can you tell what's with my way? I can't – Deniz Aug 01 '22 at 18:13

score 1 · Answer 2 · answered Aug 01 '22 at 18:11

1

You are changing an iterable as you iterate over it. That causes unpredictable behavior, like "skipping" an item in that list. There's plenty of resources on the internet describing the details (for instance).

Instead, iterate over a copy:

for each_item in numbers[:]:
    (...)

answered Aug 01 '22 at 18:11

rafaelc

57,686
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1

Thank you, your link helped a lot. – Deniz Aug 01 '22 at 18:23

Removing Duplicate Numbers in a list with a twist

2 Answers2