How to custom sort a list?-CodePudding

Is there a way to make my own sort list?

like I want to sort this :

['planets', 'animals', 'humans']
['animals', 'planets', 'humans']
['humans', 'planets', 'animals']

['humans', 'animals', 'planets']
['humans', 'animals', 'planets']
['humans', 'animals', 'planets']

CodePudding user response：

Pass a key function to sort or sorted that maps the list elements into something that has the order you want. Here's one possible solution for the example you gave:

>>> def kitaro(s):
...     return len(s), s
...
>>> sorted(['planets', 'animals', 'humans'], key=kitaro)
['humans', 'animals', 'planets']
>>> sorted(['animals', 'planets', 'humans'], key=kitaro)
['humans', 'animals', 'planets']
>>> sorted(['humans', 'planets', 'animals'], key=kitaro)
['humans', 'animals', 'planets']

Another possibility:

>>> def kitaro(s):
...     return {s: i for i, s in enumerate(
...         ['humans', 'animals', 'planets']
...     )}.get(s)
...
>>> sorted(['planets', 'animals', 'humans'], key=kitaro)
['humans', 'animals', 'planets']

CodePudding user response：

I've had to do something similar. Place each item into a list with the preferred order:

ordering_list = ['humans', 'planets', 'animals']

Translate this list into a dict of item versus priority

ordering_dict = {item: i for i, item in enumerate(ordering_list)}

Define a method to use as the sort key. For unknown values we can choose len(ordering_dict) to place these items at the back. You could also use any arbitrary value depending on your needs.

def ordering_key(item):
    return ordering_dict.get(item, len(ordering_dict))

Now sorting is easy:

import pprint


unsorted_data = [
    ['planets', 'animals', 'humans'],
    ['animals', 'planets', 'humans'],
    ['humans', 'planets', 'animals'],
    ['foo', 'planets', 'animals', 'humans'],
]

sorted_data = [
    sorted(data, key=ordering_key) for data in unsorted_data
]
pprint.pprint(sorted_data)

[['humans', 'planets', 'animals'],
 ['humans', 'planets', 'animals'],
 ['humans', 'planets', 'animals'],
 ['humans', 'planets', 'animals', 'foo']]