I am trying to find the set of lists in a tuple

Question

for example,

(['2', '3', '5'], ['1', '3', '4', '5'])

the above should yield the numbers 3 and 5

(['1', '2', '4'], ['1', '2'])

this should give out 1 , 2

(['2', '3', '5'], ['1', '2', '4'], ['2', '3'])

this, should give out 2, because 2 is contained in all 3 lists in the tuple. If there is no set it should just return an empty list

for i,e in enumerate(tup):
while index < len(tup):
    print(tup[index], tup[index + 1])
    index = index + 1

For now i have this, i am not sure how to go through the tup(Tuple) and extract each list to find the set of each 2 lists and iterate and compare with the rest of lists in the tuple

`because 2 is contained in all 3 lists in the tuple`, but `4` is not contained in both lists in the first tuple. What's the logic here? — inspectorG4dget, Feb 22 '16 at 21:07
Why should it return and empty string by default? Why not just a list with no elements? The output type is not very clear — Flavian Hautbois, Feb 22 '16 at 21:10
@FlavianHautbois sure either one is fine, but i was going to use the output for a map so it shouldn't matter — dedpo, Feb 22 '16 at 21:11

score 6 · Accepted Answer · answered Feb 22 '16 at 21:13

6

def intersect(lists):
    return list(set.intersection(*map(set, lists)))

answered Feb 22 '16 at 21:13

Julien Spronck

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I like this answer best since it's clean and it handles variable number of lists – SirParselot Feb 22 '16 at 21:14
@timgeb intersection needs sets and not lists ... you can do a list comprehension instead but i think you still need to convert them to sets – Julien Spronck Feb 22 '16 at 21:21
@JulienSpronck you are right, I misread. You can use `intersection` on an existing set without converting the arguments to sets (see my answer). – timgeb Feb 22 '16 at 21:22
@timgeb fair enough :-) – Julien Spronck Feb 22 '16 at 21:22
2

Kind of stolen from http://stackoverflow.com/questions/10861236/intersection-of-variable-number-of-lists though – Flavian Hautbois Feb 22 '16 at 21:25

score 3 · Answer 2 · answered Feb 22 '16 at 21:11

3

In [8]: t = (['2', '3', '5'], ['1', '3', '4', '5'])

In [9]: functools.reduce(lambda a,b: set.intersection(set(a), set(b)), t)
Out[9]: {'3', '5'}

answered Feb 22 '16 at 21:11

inspectorG4dget

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score 2 · Answer 3 · answered Feb 22 '16 at 21:13

Be consistent in return types. Don't return an empty string when you have an empty set.

That being said, I'd find the numbers like this:

>>> lsts = (['2', '3', '5'], ['1', '3', '4', '5'])
>>> set(lsts[0]).intersection(*lsts[1:])
set(['3', '5'])
>>> 
>>> lsts = (['1', '2', '4'], ['1', '2'])
>>> set(lsts[0]).intersection(*lsts[1:])
set(['1', '2'])
>>> 
>>> lsts = (['2', '3', '5'], ['1', '2', '4'], ['2', '3'])
>>> set(lsts[0]).intersection(*lsts[1:])
set(['2'])

The function for that would be:

>>> def common(lsts):
...     return set() if not lsts else set(lsts[0]).intersection(*lsts[1:])

score 1 · Answer 4 · answered Feb 22 '16 at 21:13

1

Simple as that: python has a set type, so just

sets = [set(l) for l in (['2', '3', '5'], ['1', '3', '4', '5']) ]
common_elements = reduce(lambda a,b: a & b, sets)

answered Feb 22 '16 at 21:13

Marcus Müller

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I am trying to find the set of lists in a tuple

4 Answers4