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How to check element of list are present in other list?

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How to check element of list are present in other list?

Nov 23rd, 2007

Hi,

I have two list of any datatype supported by python. I want to check whether the any of the element of first list
is present in second list or not.

Example: I have
a = [4,5,6]
b = [1,3,8,6,7,9]

I want to check whether any element of a is present in be or not. Also without using for loop.
Is there any other way to do this or any inbuilt function of python,which will check this. Please suggest me.

Thanks

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Re: How to check element of list are present in other list?

Nov 24th, 2007

Convert them to sets and use the intersection.

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Re: How to check element of list are present in other list?

Nov 26th, 2007

Hello,

Thanks for your reply.
Since I am new to python, i do not have any idea of sets. So It would be good for me if you can give me an example of, how to it convert in to sets and how to take the intersection.

Thanks

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Re: How to check element of list are present in other list?

Nov 26th, 2007

 Help with Code Tags 
 Python Syntax (Toggle Plain Text) 
a = [4,5,6]
s = set(a)
a = [4,5,6]
s = set(a)

Now s is a set

For further info have a look at the documentation.

Last edited by mawe; Nov 26th, 2007 at 9:31 am.

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Re: How to check element of list are present in other list?

Nov 26th, 2007

Actually there are many ways to solve this, but here would be an example for a beginning student. Study it and try to understand it ...

 Help with Code Tags 
 python Syntax (Toggle Plain Text) 
a = [4,5,6]
b = [1,3,8,6,7,9]
 
c = []
for bx in b:
    if bx in a:
        c.append(bx)
 
if c:
    print "these are the elements of list a that are present in list b:"
    print c
else:
    print "no elements of list a are in list b"
a = [4,5,6]
b = [1,3,8,6,7,9]

c = []
for bx in b:
    if bx in a:
        c.append(bx)
        
if c:
    print "these are the elements of list a that are present in list b:"
    print c
else:
    print "no elements of list a are in list b"

May 'the Google' be with you!

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Re: How to check element of list are present in other list?

Nov 26th, 2007

Nice and easy, vegaseat, but

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Originally Posted by R.S.Chourasia

Also without using for loop.

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Re: How to check element of list are present in other list?

Nov 24th, 2008

Here is the answer to do the same ...using sets..

from sets import Set
a = Set([1,2,3,4,5])
b = Set([6,7,8,9,10])
c = Set([2,4,6,8,10])
s1 = list(a.intersection(b))
s2 = list(a.intersection(c))
s3 = list(b.intersection(c))
print s1
print s2
print s3

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Re: How to check element of list are present in other list?

Feb 26th, 2009

This following if condition to check for the presence of an element in a list is just wonderful.

if bx in b:

where bx is a element that can be checked for its presence in the list b

Thank you,