How to search for an item in a list of lists?

Question

How can I do something like this.

index=[[test1,test2,test3],[test4,test5,test6],[test7,test8,test9]]
if test5 is in index:
    print True

Answer 1

try

index=[[test1,test2,test3],[test4,test5,test6],[test7,test8,test9]]
flat_index=[item for sublist in index for item in sublist]
if test5 is in flat_index:
    print True

see also Making a flat list out of list of lists in Python