Sorting a list of tuples in python according to an element index

Question

How can I sort a list of tuples according to the int in a certain position? (without a for loop)

eg. Sorting l = [(1,5,2),(7,1,4),(1,6,3)] according to the third element in each tuple?

Community · Accepted Answer · 2017-05-23 12:03:40Z

2

You can use list.sort, its key function, and operator.itemgetter:

>>> from operator import itemgetter
>>> l = [(1,5,2),(7,1,4),(1,6,3)]
>>> l.sort(key=itemgetter(2))
>>> l
[(1, 5, 2), (1, 6, 3), (7, 1, 4)]
>>>

You could also use a lambda function instead of operator.itemgetter:

>>> l = [(1,5,2),(7,1,4),(1,6,3)]
>>> l.sort(key=lambda x: x[2])
>>> l
[(1, 5, 2), (1, 6, 3), (7, 1, 4)]
>>>

However, the latter is generally faster.

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answered Feb 18, 2014 at 16:11

user2555451

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Comments

That1Guy · Accepted Answer · 2014-02-18 16:12:31Z

2

You can specify the key by which to sort a list using the sorted builtin:

>>> mylist = sorted([(1,5,2),(7,1,4),(1,6,3)], key = lambda t: t[2])
>>> mylist
[(1, 5, 2), (1, 6, 3), (7, 1, 4)]
>>>

answered Feb 18, 2014 at 16:12

That1Guy

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