Deleting elements from a list

Question

We got 2 lists, I'm trying to remove the common elements from the bigger list!

This is my code:

a =[ 2,3,4,5,1,2,3,2,3,4,5,6,7,8]
b = [2,3,4,5,2,3]
for i in range(len(b)):
if b[i] in a:
a.remove(b[i])
print(a)

But it's not true!
What's wrong with it?

Answer 1

Amirreza Hashemi ,

to do it with a loop you can use:

a =[ 2,3,4,5,1,2,3,2,3,4,5,6,7,8]
b = [2,3,4,5,2,3]

# it is important not to iterate over the original list 'a', as indexes will change by deleting elements. use a copy of list 'a[:]' to iterate over.
for num_a in a[:]: .
if num_a in b:
a.remove(num_a)
print(a)

# result is: [1, 6, 7, 8]

Answer 2

Check these links,
https://www.google.com/url?sa=t&source=web&rct=j&url=https://docs.JUMP_LINK__&&__python__&&__JUMP_LINK.org/3/tutorial/datastructures.html&ved=2ahUKEwjZpaSC14vzAhU4rZUCHUNcB1AQFnoECDUQAQ&sqi=2&usg=AOvVaw16HjD78khY_g9UUcJL3zlb

https://www.google.com/url?sa=t&source=web&rct=j&url=https://www.guru99.com/python-list-remove-clear-pop-del.html&ved=2ahUKEwjZpaSC14vzAhU4rZUCHUNcB1AQFnoECBQQAQ&sqi=2&usg=AOvVaw2WywaQUyY8fDFZYllpyVA2

"remove" method removes only first matching element.

You can however do the following instead,

a =[ 2,3,4,5,1,2,3,2,3,4,5,6,7,8]
b = [2,3,4,5,2,3]
print(list(set(a)-set(b)))

Edit: Sorry Amirreza Hashemi i just didn't thought about duplicates as mentioned by Arsalan , check Lothar code for correct answer .

Answer 3

In the Abhay's solution, the duplicate items of the list 'a' are also removed. For example if there are two 7s in the a, there will be only one 7 in the output.
In addition to the Lothar's solution, you can also use this:
c = [x for x in a if x not in b]

Answer 4

Arsalan thks for correcting me!