CODEWITHSUNDEEP
pythonlistsorting
David M
David M

Reputation: 149

Python - sort list of list

I have a list in this format:

exon_start exon_finish gene_name (repeated hundreds of times)

I want to sort by exon_start

Example list:

 ['8342758', '8344137', 'NM_001042682']
 ['85420368', '85421471', 'NM_032184']
 ['86363115', '86364485', 'NM_152890']
 ['89820771', '89822936', 'NM_015350']
 ['904123', '905900', 'NR_027693']
 ['91176416', '91179454', 'NM_201269']
 ['92418409', '92420740', 'NM_015237']
 ['93575521', '93577419', 'NR_034089']
 ['94114411', '94116006', 'NM_014597']
 ['99926918', '99928016', 'NM_017734']

This list of lists (printed above) has already been sorted with the following code:

sorted_triplets = sorted(triplets, key=lambda x: x[0])
for i in sorted_triplets:
    print i

However, "sorted" isn't working like I expect. As you can see from the list, 904123 is less than 89820771. So it appears that "sorted" isn't comparing the numbers as a whole, rather as individual digits.

How do I fix this?

Upvotes: 0

Views: 1633

Answers (6)

TerjeR
TerjeR

Reputation: 154

Add int() call.

sorted_triplets = sorted(triplets, key=lambda x: int(x[0]))

Upvotes: 0

Martin Thoma
Martin Thoma

Reputation: 136237

It seems like your "number" is actually a string. Convert this string to an integer ( int(string) ), then the sorting should work

Upvotes: 0

Keith
Keith

Reputation: 43024

Right, because what you have are strings, not numbers. It will be sorted lexicographically. You may want to convert them to numbers (integers) first.

Upvotes: 0

Andrey Sboev
Andrey Sboev

Reputation: 7672

convert strings to numbers

sorted(triplets, key=lambda x: int(x[0]))

Upvotes: 1

drewrobb
drewrobb

Reputation: 1604

Convert exon_start to an integer, strings are sorted lexicographically.

Upvotes: 0

colinmarc
colinmarc

Reputation: 2471

It's sorting them as strings, so the order is 'alphabetically'. Which is to say, it's going character by character and comparing, instead of comparing them as scalar values.

So do:

sorted_triplets = sorted(triplets, key=lambda x: int(x[0]))

And it should work.

Upvotes: 4

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