Case insensitive matching python

Question

I want to match items from one list in another without worrying about case sensitivity.

mylist1 = ['fbH_q1ba8', 'fHh_Q1ba9', 'fbh_q1bA10','hoot']
mylist2 = ['FBH_q1ba8', 'trick','FBH_q1ba9', 'FBH_q1ba10','maj','joe','civic']

I was doing this before:

for item in mylist2:
    if item in mylist1:
        print "true"
    else:
        print "false"

But this fails because it is not case sensitive.

I am aware of re.match(“TeSt”, “Test”, re.IGNORECASE) but how can I apply that to my example?

Asked By: Boosted_d16

||

Source

Answer 1

Normalize the case with str.lower():

for item in mylist2:
    print item.lower() in mylist1

The in containment operator already returns True or False, easiest just to print that:

>>> mylist1 = ['fbh_q1ba8', 'fhh_q1ba9', 'fbh_q1ba10','hoot']
>>> mylist2 = ['FBH_q1ba8', 'trick','FBH_q1ba9', 'FBH_q1ba10','maj','joe','civic']
>>> for item in mylist2:
...     print item.lower() in mylist1
... 
True
False
False
True
False
False
False

If mylist1 contains mixed case values, you’ll need to make the loop explicit; use a generator expression to produce lowercased values; testing against this ensures only as many elements are lowercased as needed to find a match:

for item in mylist2:
    print item.lower() in (element.lower() for element in mylist1)

Demo

>>> mylist1 = ['fbH_q1ba8', 'fHh_Q1ba9', 'fbh_q1bA10','hoot']
>>> for item in mylist2:
...     print item.lower() in (element.lower() for element in mylist1)
... 
True
False
False
True
False
False
False

Another approach is to use any():

for item in mylist2:
    print any(item.lower() == element.lower() for element in mylist1)

any() also short-circuits; as soon as a True value has been found (a matching element is found), the generator expression iteration is stopped early. This does have to lowercase item each iteration, so is slightly less efficient.

Another demo:

>>> for item in mylist2:
...     print any(item.lower() == element.lower() for element in mylist1)
... 
True
False
False
True
False
False
False

Answered By: Martijn Pieters

Answer 2

Why not just do:

for item in mylist2:
    if item.lower() in [j.lower() for j in mylist1]:
        print "true"
    else:
        print "false"

This uses .lower() to make the comparison which gives the desired result.

Answered By: sshashank124

Answer 3

The other answers are correct. But they dont account for mixed cases in both lists. Just in case you need that:

mylist1 = ['fbh_q1ba8', 'fbh_q1ba9', 'fbh_q1ba10','hoot']
mylist2 = ['FBH_q1ba8', 'trick','FBH_q1ba9', 'FBH_q1ba10','maj','joe','civic']

for item in mylist2:
    found = "false"
    for item2 in mylist1:
        if item.lower() == item2.lower():
            found = "true"
    print found

Answered By: Martyn

Case insensitive matching python

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