问题
How do you find or keep only the sublists of a list if it the sublist is also present within another list?
lsta = [['a','b','c'],['c','d','e'],['e','f','g']]
lstb = [['a','b','c'],['d','d','e'],['e','f','g']]
I'd like to do something like set(lsta) & set(lstb)
Desired_List = [['a','b','c'],['e','f','g']]
The reason I'd like to do something like set is for it's speed as I'm doing this on a very large list where efficiency is quite important.
Also, slightly unrelated, what if I wanted to subtract lstb from lsta to get
Desired_List2 = [['d','d','e']]
回答1:
Better change the list of lists to list of tuples, then you can easily use the set operations:
>>> tupa = map(tuple, lsta)
>>> tupb = map(tuple, lstb)
>>> set(tupa).intersection(tupb)
set([('a', 'b', 'c'), ('e', 'f', 'g')])
>>> set(tupa).difference(tupb)
set([('c', 'd', 'e')])
回答2:
If your sub-lists need to remain lists, use a list comprehension
Intersection:
>>> [i for i in lsta if i in lstb]
[['a', 'b', 'c'], ['e', 'f', 'g']]
Subtraction:
>>> [i for i in lsta if i not in lstb]
[['c', 'd', 'e']]
回答3:
I have written a C module a while ago for this:
>>> lsta = [['a','b','c'],['c','d','e'],['e','f','g']]
>>> lstb = [['a','b','c'],['d','d','e'],['e','f','g']]
>>> list(boolmerge.andmerge(lsta, lstb))
>>> import boolmerge
[['a', 'b', 'c'], ['e', 'f', 'g']]
This is O(n) time, and require the lists to be sorted.
来源：https://stackoverflow.com/questions/21448310/how-do-you-find-common-sublists-between-two-lists