How can I sort list of strings in specific order?

Question

Let's say I have such a list:

['word_4_0_w_7',
 'word_4_0_w_6',
 'word_3_0_w_10',
 'word_3_0_w_2']

and I want to sort them according to number that comes after "word" and according to number after "w". It will look like this:

   ['word_3_0_w_2',
     'word_3_0_w_10',
     'word_4_0_w_6',
     'word_4_0_w_7']

What comes in mind is to create a bunch of list and according to index after "word" stuff them with sorted strings according "w", and then merge them.

Is in Python more clever way to do it?

Answer 1

Use Python's key functionality, in conjunction with other answers:

def mykey(value):
    ls = value.split("_")
    return int(ls[1]), int(ls[-1])

newlist = sorted(firstlist, key=mykey)
## or, if you want it in place:
firstlist.sort(key=mykey)

Python will be more efficient with key vs cmp .

Answer 2

You can use a function to extract the relevant parts of your string and then use those parts to sort:

a = ['word_4_0_w_7', 'word_4_0_w_6', 'word_3_0_w_10', 'word_3_0_w_2']

def sort_func(x):
    parts = x.split('_');
    sort_key = parts[1]+parts[2]+"%02d"%int(parts[4])
    return sort_key

a_sorted = sorted(a,key=sort_func)

The expression "%02d" %int(x.split('_')[4]) is used to add a leading zero in front of second number otherwise 10 will sort before 2 . You may have to do the same with the number extracted by x.split('_')[2] .

Answer 3

You can provide a function to the sort() method of list objects:

l = ['word_4_0_w_7',
     'word_4_0_w_6',
     'word_3_0_w_10',
     'word_3_0_w_2']

def my_key_func(x):
    xx = x.split("_")
    return (int(xx[1]), int(xx[-1]))
l.sort(key=my_key_func)

Output:

print l
['word_3_0_w_2', 'word_3_0_w_10', 'word_4_0_w_6', 'word_4_0_w_7']

edit : Changed code according to comment by @dwanderson ; more info on this can be found here .