CODEWITHSUNDEEP
pythonlistsortingtuples
Haryo Dollybim
Haryo Dollybim

Reputation: 99

get all tuples with maximum second value

How to fix the number of occurrence in a list of tuples and return an item with max value.

        given = [('a',2),('b',3),('c',5),('a',3),('c',5)]

        expected = [('c',5),('a',3),('b',3)]

How do you do this without doing anything to complex.

Upvotes: 0

Views: 65

Answers (4)

RoadRunner
RoadRunner

Reputation: 26315

A very straightforward approach is to group the tuples in a dictionary, then just get the maximum (letter, number) value from each letter key in the dictionary:

from collections import defaultdict
from operator import itemgetter

given = [('a',2),('b',3),('c',5),('a',3),('c',5)]

d = defaultdict(list)
for key, value in given:
    d[key].append((key, value))

>>> print(dict(d))
{'b': [('b', 3)], 'a': [('a', 2), ('a', 3)], 'c': [('c', 5), ('c', 5)]}

>>> print([max(x[1], key = itemgetter(1)) for x in sorted(d.items())])
[('a', 3), ('b', 3), ('c', 5)]

Without using external libraries:

given = [('a',2),('b',3),('c',5),('a',3),('c',5)]

d = {}
for key, value in given:
    if key not in d:
        d[key] = []
    d[key].append((key, value))

>>> print(d)
{'b': [('b', 3)], 'a': [('a', 2), ('a', 3)], 'c': [('c', 5), ('c', 5)]}

>>> print([max(x[1], key = lambda x: x[1]) for x in sorted(d.items())])
[('a', 3), ('b', 3), ('c', 5)]

Upvotes: 1

Haryo Dollybim
Haryo Dollybim

Reputation: 99

        given = [('a',2),('b',3),('c',5),('a',3),('c',5)]
        expected = dict(given).items()
        dict_items([('a', 3), ('b', 3), ('c', 5)])

Upvotes: -1

plasmon360
plasmon360

Reputation: 4199

from itertools import groupby
groups = groupby(sorted(given, key = lambda x: x[0]), key = lambda x: x[0])
print [max(g) for k,g in groups]

results in 

[('a', 3), ('b', 3), ('c', 5)]

Upvotes: 2

smac89
smac89

Reputation: 43186

Here is one way:

given = [('a',2),('b',3),('c',5),('a',3),('c',5)]
expected = dict(sorted(given)).items()

Explanation

sorted(...)

When you sort the list, all the items with a low value (second element) are moved to the front of the list.

dict(...)

When you convert the sorted list to a dict, the lower values are replaced by the higher values which are closer to the end of the list.

Upvotes: 1

Related Questions