Welcome to OGeek Q&A Community for programmer and developer-Open, Learning and Share
Welcome To Ask or Share your Answers For Others

Categories

0 votes
430 views
in Technique[技术] by (71.8m points)

python - Get tuples with max value from each key from a list

I have a list of tuples like this:

[(1, 0), (2, 1), (3, 1), (6, 2), (3, 2), (2, 3)]

I want to keep the tuples which have the max first value of every tuple with the same second value. For example (2, 1) and (3, 1) share the same second (key) value, so I just want to keep the one with the max first value -> (3, 1). In the end I would get this:

[(1, 0), (3, 1), (6, 2), (2, 3)]

I don't mind at all if it is not a one-liner but I was wondering about an efficient way to go about this...

See Question&Answers more detail:os

与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…
Welcome To Ask or Share your Answers For Others

1 Reply

0 votes
by (71.8m points)
from operator import itemgetter
from itertools import groupby

[max(items) for key, items in groupby(L,key = itemgetter(1))]

It's assuming that you initial list of tuples is sorted by key values.

groupby creates an iterator that yields objects like (0, <itertools._grouper object at 0x01321330>), where the first value is the key value, the second one is another iterator which gives all the tuples with that key.

max(items) just selects the tuple with the maximum value, and since all the second values of the group are the same (and is also the key), it gives the tuple with the maximum first value.

A list comprehension is used to form an output list of tuples based on the output of these functions.


与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…
OGeek|极客中国-欢迎来到极客的世界,一个免费开放的程序员编程交流平台!开放,进步,分享!让技术改变生活,让极客改变未来! Welcome to OGeek Q&A Community for programmer and developer-Open, Learning and Share
Click Here to Ask a Question

...