根据列表Python中的特定部分对列表进行排序

Question

I have a list in the format:

Apple, Orange[123 431]43351
Banana, Cherry[141 421]23423
Coconut, Mango[23 12312]232342
....
....

I want to sort the list according to the number after the bracket ']'. The output should be:

Banana, Cherry[141 421]23423 
Apple, Orange[123 431]43351 
Coconut, Mango[23 12312]232342

I am trying to sort the list by using this:

LIST.sort(key = lambda x: x.split()[1])
for item in LIST:
    print(item)

I can find the last number by this: But I am not able to sort it

for item in LIST:
    bracket_index = item.find("]")
    end_of_line = item[bracket_index + 1:]
    if bracket_index != -1:
        print(end_of_line)

Answer 1

What is the format of your list? Is it a list of tuples or a list of strings? This works:

a = ['Apple, Orange[123 431]43351',
'Banana, Cherry[141 421]23423',
'Coconut, Mango[23 12312]232342']

a.sort(key = lambda el: el.split(']')[1])
print(a)

Output:
 ['Coconut, Mango[23 12312]232342',
 'Banana, Cherry[141 421]23423',
 'Apple, Orange[123 431]43351']

If it is a list of pairs of strings instead, then you should use key = lambda el: el[1].split(']')[1] like so:

a = [('Apple', 'Orange[123 431]43351'),
('Banana', 'Cherry[141 421]23423'),
('Coconut',' Mango[23 12312]232342')]

a.sort(key = lambda el: el[1].split(']')[1])
print(a)

Output:
[('Coconut', ' Mango[23 12312]232342'),
 ('Banana', 'Cherry[141 421]23423'),
 ('Apple', 'Orange[123 431]43351')]

Answer 2

You can go with @Psidom's suggestion:

LIST.sort(key=lambda x: int(x.split(']')[1]))

Notice the use of int() to ensure the sort is done numerically rather than by string comparisons (which are done lazily; ie, '4321' is considered "larger" than '20000000' due to '4' > '2' ).

---

Full example:

LIST = [
    'Apple, Orange[123 431]43351',
    'Banana, Cherry[141 421]23423',
    'Coconut, Mango[23 12312]232342'
]

LIST.sort(key=lambda x: int(x.split(']')[1]))
print(LIST)

---

A better method would be to parse your strings first. For example:

from collections import namedtuple
import re

FruitTuple = namedtuple('FruitTuple', ['fruit', 'color', 'num1', 'num2', 'num3'])

unparsed_list = [
    'Apple, Orange[123 431]43351',
    'Banana, Cherry[141 421]23423',
    'Coconut, Mango[23 12312]232342'
]

split_list = [re.search('(\\w+), (\\w+)\\[(\\d+) (\\d+)\\](\\d+)', x).groups() for x in unparsed_list]
fruit_list = [FruitTuple(*x) for x in split_list]
fruit_list.sort(key=lambda x: int(x.num2))

print(fruit_list)

Produces:

[FruitTuple(fruit='Banana', color='Cherry', num1='141', num2='421', num3='23423'), FruitTuple(fruit='Apple', color='Orange', num1='123', num2='431', num3='43351'), FruitTuple(fruit='Coconut', color='Mango', num1='23', num2='12312', num3='232342')]