How to sort a list by an int-based string inside the list?

Question

I've been having some issues with some code lately and thought I'd share with this amazing community!

I have a list of strings, that are also string-based lists, delimited by a special character ('~'). For example..

list1 = [
'0~A~Sometext',
'56~B~Sometext',
'3~A~Sometext',
'875~G~Sometext',
'54~V~Sometext',
'3~D~Sometext',
'20~S~Sometext',
'7~R~Sometext'
]

I would like to sort this list based off the first element in the string (0,56,3,875,etc...)

When I try to implement my own sorting algorithm or use Python's sort, it doesn't output the correct order.

score 3 · Accepted Answer · answered Oct 18 '19 at 16:25

You can use a custom function for the sorting, by passing it as the key argument for the sort() method:

list1 = [
    '0~A~Sometext',
    '56~B~Sometext',
    '3~A~Sometext',
    '875~G~Sometext',
    '54~V~Sometext',
    '3~D~Sometext',
    '20~S~Sometext',
    '7~R~Sometext'
]
list1.sort(key=lambda x: int(x.split('~')[0]))
print(list1)

This will take every element:

Split it around the ~, so that '0~A~Sometext' becomes ['0', 'A', 'Sometext']
Take the first element from that list
Make it an integer.

And compare all of those integers to sort the list.

Output:

['0~A~Sometext', '3~A~Sometext', '3~D~Sometext', '7~R~Sometext', '20~S~Sometext', '54~V~Sometext', '56~B~Sometext', '875~G~Sometext']

Thank you so much, I believe I was comparing based on the string implementation of the int, instead of an actual int. Thank you! — Jonathan Sanchez, Oct 18 '19 at 16:37

score 2 · Answer 2 · answered Oct 18 '19 at 16:27

2

You can define your own sort key and specify it in the sort method.

e.g.

def sort_key(input):
    return int(input.split('~')[0])

list1.sort(key=sort_key)

answered Oct 18 '19 at 16:27

WhatAmIDoing

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How to sort a list by an int-based string inside the list?

2 Answers2