How to find the maximum value in a list of tuples?

I have a list with ~10^6 tuples in it like this:

[(101, 153), (255, 827), (361, 961), ...]
^     ^
X     Y

I want to find the maximum value of the Ys in this list, but also want to know the X that it is bound to.

How do I do this?

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最佳答案

Use max():

 
Using itemgetter():

In [53]: lis=[(101, 153), (255, 827), (361, 961)]


In [81]: from operator import itemgetter


In [82]: max(lis,key=itemgetter(1))[0]    #faster solution
Out[82]: 361

using lambda:

In [54]: max(lis,key=lambda item:item[1])
Out[54]: (361, 961)


In [55]: max(lis,key=lambda item:item[1])[0]
Out[55]: 361

timeit comparison:

In [30]: %timeit max(lis,key=itemgetter(1))
1000 loops, best of 3: 232 us per loop


In [31]: %timeit max(lis,key=lambda item:item[1])
1000 loops, best of 3: 556 us per loop
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You could loop through the list and keep the tuple in a variable and then you can see both values from the same variable...

num=(0, 0)
for item in tuplelist:
if item[1]>num[1]:
num=item #num has the whole tuple with the highest y value and its x value
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In addition to max, you can also sort:

>>> lis
[(101, 153), (255, 827), (361, 961)]
>>> sorted(lis,key=lambda x: x[1], reverse=True)[0]
(361, 961)

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