Python - comparing two nested lists and writing a third nested list

Question

some_list = [[app_num, product, prod_size, prod_amt]]
other_list = [[app_num, product, prod_size, prod_amt]]

I have two lists of lists. There are no matches between some_list and other_list for app_num. However, for a given app_num in other_list, the product, prod_size_ and prod_amt may be the same as in a given app_num in some_list. I am trying to create a final_some_list that is the same as some_list, except that it has deleted any list element from some_list if that list element has the same product, prod_size, and prod_amt as an element in other_list.

I have tried nested for loops, list comprehension (below are some examples of many failed attempts).

final_some_list = [app for app in some_list for other_app in other_list 
if not app[1] == other_app[1] and app[2] == other_app[2] and app[3] == 
other_app[3]

final_some_list = [app for app in some_list for other_app in other_list 
if not app[1] and app[2] and app[3] == in other_app

Can you share an example of input and desired output so that it makes easier for anyone to understand your question? — Bernardo Duarte
– Bernardo Duarte, Commented Sep 23, 2017 at 0:36

Elmex80s · Accepted Answer · 2019-01-02 22:29:12Z

4

final_some_list = [x for x in some_list if all(x[1:] != y[1:] for y in other_list)]

Edit:

Solution above is O(nm) where n == len(some_list) and m == len(other_list). You can make it O(n log m) if you want. Put all the tails of all the elements of other_list in a binary search tree (assuming those elements are ordable), now querying that tree is O(log m). In case the elements are hashable you can even have an O(n) solution because querying a hash-set is O(1).

Btw: The elements of both lists look like tuples to me, this will get you more close to a better solution.

edited Jan 2, 2019 at 22:29

answered Sep 23, 2017 at 2:04

Elmex80s

3,5041 gold badge17 silver badges25 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

pale bone · Accepted Answer · 2017-09-23 00:15:33Z

0

Only the first comparison contains the notattribute, add != to all of the comparisons and this should work:

final_some_list = [app for app in some_list for other_app in other_list 
if app[1] != other_app[1] and app[2] != other_app[2] and app[3] != 
other_app[3]]

answered Sep 23, 2017 at 0:15

pale bone

1,8462 gold badges22 silver badges29 bronze badges

Collectives™ on Stack Overflow

Python - comparing two nested lists and writing a third nested list

2 Answers 2

Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related