how to sort list in python which has two numbers per index value?

Question

My code

b=[((1,1)),((1,2)),((2,1)),((2,2)),((1,3))] for i in range(len(b)): print b[i] Obtained output:
(1, 1)
(1, 2)
(2, 1)
(2, 2)
(1, 3)

how do i sort this list by the first element or/and second element in each index value to get the output as:
(1, 1)
(1, 2)
(1, 3)
(2, 1)
(2, 2)

OR

(1, 1)
(2, 1)
(1, 2)
(2, 2)
(1, 3)

It would be nice if both columns are sorted as shown in the desired output, how ever if either of the output columns is sorted it will suffice.

Idos · Accepted Answer · 2015-12-06 16:30:20Z

1

Try this: b = sorted(b, key = lambda i: (i[0], i[1]))

answered Dec 6, 2015 at 16:30

Idos

15.3k14 gold badges63 silver badges81 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

mrd · Accepted Answer · 2015-12-06 16:44:59Z

0

The sorted builtin does this.

>>> sorted (b)
[(1, 1), (1, 2), (1, 3), (2, 1), (2, 2)]

This only sorts by the first element, to sort on the second

>>> sorted(b, key=lambda i: i[1])
[(1, 1), (2, 1), (1, 2), (2, 2), (1, 3)]

Also notice that Python doesn't allow this nested tuple; the paren inside a paren is reduced to just one.

>>> b=[((1,1)),((1,2)),((2,1)),((2,2)),((1,3))]
>>> b
[(1, 1), (1, 2), (2, 1), (2, 2), (1, 3)]

answered Dec 6, 2015 at 16:39

mrd

1412 silver badges8 bronze badges