Sorting list-within-list in Python

Question

I have a list within a list that is in this format:

[['39.9845450804', '-75.2089337931', 'Paved', ' ', 5.974380011873201],
['39.977111208', '-75.1326105278', 'Asphalt', '8', 3.4881723880136537],
['39.9767607107', '-75.1328155113', 'Asphalt', '20', 1.5123970222417986],
['40.089750884', '-74.9852538861', 'Paved', ' ', 4.296923142303416]]

Where the indices are latitude, longitude, type of pavement, no. of empty spots, and location in KM from my current location

I want to sort this unsorted list from the greatest to lowest by my 4-th index, which is the location in KM from my current location. You can assume that the list-within-list will will contains the same total number of data points of five.

I know to use sort() for single-dimensional lists, but I am not quite sure how to sort lists within lists.

Any assistance is appreciated.

possible duplicate of Python - sort list of list

Jose Ricardo Bustos M.
– Jose Ricardo Bustos M.

2015-04-25 20:26:40 +00:00
Commented Apr 25, 2015 at 20:26 — Jose Ricardo Bustos M.
– Jose Ricardo Bustos M., Commented Apr 25, 2015 at 20:26

Benjy Kessler · Accepted Answer · 2015-04-25 20:18:30Z

3

If my_data is your list then to sort by the 5th element in my_data you do:

sorted(my_data, key=lambda data: data[4])

edited Apr 25, 2015 at 20:18

answered Apr 25, 2015 at 20:17

Benjy Kessler

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Dair · Accepted Answer · 2015-04-25 20:17:55Z

2

Use the key parameter:

a = [['39.9845450804', '-75.2089337931', 'Paved', ' ', 5.974380011873201],
['39.977111208', '-75.1326105278', 'Asphalt', '8', 3.4881723880136537],
['39.9767607107', '-75.1328155113', 'Asphalt', '20', 1.5123970222417986],
['40.089750884', '-74.9852538861', 'Paved', ' ', 4.296923142303416]]

sorted(a, key=lambda entry: entry[4])

Gives:

[['39.9767607107', '-75.1328155113', 'Asphalt', '20', 1.5123970222417986], ['39.977111208', '-75.1326105278', 'Asphalt', '8', 3.4881723880136537], ['40.089750884', '-74.9852538861', 'Paved', ' ', 4.296923142303416], ['39.9845450804', '-75.2089337931', 'Paved', ' ', 5.974380011873201]]

answered Apr 25, 2015 at 20:17

Dair

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Comments

ovgolovin · Accepted Answer · 2015-04-25 20:20:16Z

1

There is a key argument in sort:

from operator import itemgetter
data.sort(key=itemgetter(4))

answered Apr 25, 2015 at 20:20

ovgolovin

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1 Comment

tommy.carstensen Over a year ago

And operator.itemgetter() is also documented here.

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