performance - Compare two lists in python and print the output -

hi have list of lists , need compare value of each list 1 extracted xml file. structure similar this:

[('example', '123', 'foo', 'bar'), ('example2', '456', 'foo', 'bar'), ...] 

i need compare second value of each list values in xml:

for item in main_list:     child in xml_data:         if item[4] == child.get('value'):             print item[4] 

the problem main_list has huge ammount of lines (1000+) , multiplied values xml (100+) results in lot of iterations becoming method unefficient.

is there way efficiently?

regards.

a membership check on set faster manually iterating , checking:

children = {child.get('value') child in xml_data} item in main_list:     if item[4] in children:         print(item[4]) 

here construct set simple set comprehension.

note may worth swapping data in set - if main_list longer, more efficient make set of data.

items = {item[4] item in main_list} child in xml_data:     value = child.get('value')     if value in items:         print(value) 

these both processing on data once, rather each time check made.

note set not handle duplicate values or order on set side - if important, isn't valid solution. version use order/duplicates data iterating over. if isn't valid, can still process data beforehand, , use itertools.product() iterate little quicker.

items = [item[4] item in main_list] children = [child.get('value') child in xml_data]  item, child in itertools.product(items, children):     if item == child:         print(item) 

as karl knechtel points out, if don't care order duplicates at all, can set intersection:

for item in ({child.get('value') child in xml_data} &              {item[4] item in main_list}):     print(item)