Python remove element in list

Question

I have a question

say I have two list, and each of them contains couple of strings

a = ['x', 'y', 'z', 't'] b = ['xyz', 'yzx', 'xyw']

I want to delete xyw in list b, because w is not in list a.

I tried

for s in a:
    k = [t for t in b if t.find(s)]

but it didn't work Does anyone know how to do this in Python? Thank you!

I'm sorry but as SO is not a do it for me site you need to show us that what you have tried so far! then we can help you on your problems! — Kasravnd
– Kasravnd, Commented Feb 17, 2015 at 16:22
@KasraAD thanks for your reminder, I just join this website. I did have a try, I changed my question. — Ningxi
– Ningxi, Commented Feb 17, 2015 at 16:35
welcome! OK, always remember that as you explain more about your question as you get a complete answer! — Kasravnd
– Kasravnd, Commented Feb 17, 2015 at 16:37

Cory Kramer · Accepted Answer · 2015-02-17 16:29:43Z

3

You could check that all of the letters in each string are contained in your list a then filter out strings using a list comprehension.

>>> a = ['x', 'y', 'z']
>>> b = ['xyz', 'yzx', 'xyw']
>>> [i for i in b if all(j in a for j in i)]
['xyz', 'yzx']

edited Feb 17, 2015 at 16:29

answered Feb 17, 2015 at 16:21

Cory Kramer

119k19 gold badges176 silver badges233 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

Ningxi Over a year ago

Great! But if a = ['x', 'y', 'z', 't'], how to change the code? thanks!

Ningxi Over a year ago

I tried , but the answer is [] ... I also tried [i for i in b if any(j in i for j in a)], the answer is ['xyz', 'yzx', 'xyw'] ...

BigTailWolf · Accepted Answer · 2015-02-17 19:43:30Z

1

>>> a = ['x', 'y', 'z']
>>> b = ['xyz', 'yzx', 'xyw']
>>> for element in b:
...     if not all(i in a for i in element):
...         b.remove(element)
... 
>>> b
['xyz', 'yzx']
>>>

Correcttion: I shouldn't delete during iterating. So following like the solution above fits

>>> a = ['x', 'y', 'z']
>>> b = ['xyz', 'yzx', 'xyw']
>>> b = [i for i in b if all(j in a for j in i)]
>>> b
['xyz', 'yzx']
>>>

edited Feb 17, 2015 at 19:43

answered Feb 17, 2015 at 16:33

BigTailWolf

1,0288 silver badges18 bronze badges

2 Comments

Zero Piraeus Over a year ago

This fails for e.g. b = ['xyz', 'yzx', 'xyw', 'xyq'], because you're removing items from the list as you iterate over it.

BigTailWolf Over a year ago

@ZeroPiraeus Oh, I got. I shouldn't do that. I should follow the above solution and reassign to b. Is that correct?

Collectives™ on Stack Overflow

Python remove element in list

2 Answers 2

2 Comments

2 Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

2 Comments

2 Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related