Subtract elements in first list from the second list

Question

Let's say I have two lists: full_links & href_links

I want to remove values in href_links which contain duplicate values from full_links

For example:

full_links = [ 1,2,3,4,5]
href_links = [ 1,2,7,8,9,3]

So, the output should be:

comb_list = [7,8,9]

My code is:

comb_list = list(set(full_links) - set(href_links))

But it is not working.

Answer 1

It should be the other way round

>>> full_links = [ 1,2,3,4,5]
>>> href_links = [ 1,2,7,8,9,3]
>>> comb_list = list(set(full_links)  - set(href_links))
>>> comb_list
[4, 5]
>>> comb_list = list(set(href_links)  - set(full_links))
>>> comb_list
[8, 9, 7]

Answer 2

To take out/remove X from Y , you subtract X from Y : Y - X

comb_list = list(set(href_links) - set(full_links))

You want to remove (elements of) full_links from href_link , also called difference:

comb_list = list(set(href_links).difference(set(full_links)))

---

If you need to save the order,

>>> full_links = [1,2,3,4,5]
>>> href_links = [1,2,7,8,9,3]
>>> full_set = set(full_links)
>>> [i for i in href_links if i not in full_set]
[7, 8, 9]

Also, there is no need to construct 2 sets if you use the difference method:

>>> list(set(href_links).difference(full_links))
[7, 8, 9]

Answer 3

因为它是倒退的！

comb_list = list(set(href_links) - set(full_links))