For loop checking if not in list not working?

Asked Jun 26 '18 at 19:28

Active Jun 26 '18 at 19:30

Viewed 51 times

I have:

a=['a','v','c']  
b = ['d','a','c', 'e', 'b']

What I wanted to do was

for x in b:
    if x in a:
        b.remove(x)

But when I run this I get

b=['a','c','b']

I saw elsewhere a few ways you could modify it but none of them seem to be working. For some reason when I add a print statement right below the "for" line. It only prints out 'd', 'c', 'e'. Why are the other two elements not being reached?

I was able to solve this by doing

b = [x for x in b if x in a]

but why wasn't it working in the first place?

edited Jun 26 '18 at 19:30

asked Jun 26 '18 at 19:28

John Smith

2

Don't change the lengths of lists while iterating over them, it often leads to unexpected results. – jonrsharpe Jun 26 '18 at 19:29
It's bad practice to loop AND remove from the same list. – ltd9938 Jun 26 '18 at 19:29
1

`list(set(b) - set(a))`… – deceze Jun 26 '18 at 19:29
Both Python2 and Python3 set `b` to `['d', 'c', 'e', 'b']` in your example. Can you kindly provide exact tested values when formulating a problem? – bipll Jun 26 '18 at 19:34

For loop checking if not in list not working?

0 Answers0