CODEWITHSUNDEEP
pythonlistfor-looplist-comprehension
Srivatsan
Srivatsan

Reputation: 9363

Python, removing similar values from two lists

I have two lists, let's call them list1 and list2.

list1 is the main list which contains all the values of my data.

list2 contains certain values that have to be removed from list1. (You can say it is sort of like a sublist of list1) 

len(list1) = 13357
len(list2) = 1751

So to remove values of list2 from list1 I do:

new_list = [x for x in list1 if x not in list2]

So what you would expect is for new_list to have a length:

len(new_list) = len(list1) - len(list2) = 13357 - 1751 = 11606

However my new_list has a length = 11584 !!!

How is this possible????!!!!!

EDIT: I obtained my list2 from list1 using a calculation. I also checked for similar values using set(list1) & set(list2)

list2 is actually a quadrant of list1, it is a follow up of THIS QUESTION I had asked previously. So from the above link you can see that I have RA and DEC co-ordinates of my data. In the example, assume list1 is my RA.

So once I have my quandrants, I apply:

for a,b in zip(sliceno,list1):
    if a == 0:
        list2.append(a)

I know this is a follow-up of my previous question, so please bare with the complications!!

Upvotes: 2

Views: 164

Answers (1)

juanmajmjr
juanmajmjr

Reputation: 1163

This is almost for sure that list2 has 11606 - 11584 = 22 repeated elements. (And because of list2 is a subset of list1 then they exist also in list1)

Upvotes: 2

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