comparing strings in list to strings in list

Question

I see that the code below can check if a word is

list1 = 'this'
compSet = [ 'this','that','thing' ]
if any(list1 in s for s in compSet): print(list1)

Now I want to check if a word in a list is in some other list as below:

list1 = ['this', 'and', 'that' ]
compSet = [ 'check','that','thing' ]

What's the best way to check if words in list1 are in compSet, and doing something over non-existing elements, e.g., appending 'and' to compSet or deleting 'and' from list1?

__________________update___________________

I just found that doing the same thing is not working with sys.path. The code below sometimes works to add the path to sys.path, and sometimes not.

myPath = '/some/my path/is here'
if not any( myPath in s for s in sys.path):
    sys.path.insert(0, myPath)

Why is this not working? Also, if I want to do the same operation on a set of my paths,

myPaths = [ '/some/my path/is here', '/some/my path2/is here' ...]

How can I do it?

Re your update, what is not working? Is it giving an error? Perhaps you are just not using backslashes in your myPath variable? — brianpck
– brianpck, Commented Sep 28, 2016 at 21:00
@brianpck Thanks, I updated. The function above to add a path to sys.path works inconsistently. It works sometimes and sometimes not. Maybe it is a specific problem of my environment, I guess... By the way, If I do this adding to path thing over a list of paths with sys.path, is Intersection function is the best to do it? — noclew
– noclew, Commented Sep 28, 2016 at 22:16
If you want to find the paths that are in both lists, then yes, intersection is the best way. With regard to sys.path, I recommend asking another question if this is an issue since it's really a separate issue. — brianpck
– brianpck, Commented Sep 28, 2016 at 23:45

brianpck · Accepted Answer · 2016-09-28 20:44:22Z

8

There is a simple way to check for the intersection of two lists: convert them to a set and use intersection:

>>> list1 = ['this', 'and', 'that' ]
>>> compSet = [ 'check','that','thing' ]
>>> set(list1).intersection(compSet)
{'that'}

You can also use bitwise operators:

Intersection:

>>> set(list1) & set(compSet)
{'that'}

Union:

>>> set(list1) | set(compSet)
{'this', 'and', 'check', 'thing', 'that'}

You can make any of these results a list using list().

edited Sep 28, 2016 at 20:44

answered Sep 28, 2016 at 20:35

brianpck

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2 Comments

noclew Over a year ago

Thank you so much!

noclew Over a year ago

Hi Brian, I just updated my question. Can you please look into it?

coder · Accepted Answer · 2016-09-28 20:35:14Z

1

Try that:

 >>> l = list(set(list1)-set(compSet))
 >>> l
 ['this', 'and']

answered Sep 28, 2016 at 20:35

coder

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1 Comment

Ted Klein Bergman Over a year ago

Just to clarify; this is showing the words in list1 that is not in compSet, and not which words that is in it.

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