How can I sort given a specific order that I provide

Question

I am trying to sort files in a directory given their extension, but provided an order that I give first. Let's say I want the extension order to be

ext_list = [ .bb, .cc , .dd , aa ]

The only way that I can think of would be to go through every single file and place them in a list every time a specific extension is encountered.

for subdir, dirs, files in os.walk(directory): 
     if file.endswith( '.bb') --> append file
     then go to the end of the directory
     then loop again
     if file.endswith( '.cc')  -->append file
     and so on...
return sorted_extension_list

and then finally

        for file in sorted_extension_list :
            print file

Why are you not getting the whole list in one shot and then check the extension of each? Doing so you will get only one time the complete list and you can work on that. Hope this help to get your idea done. — Marco smdm, Apr 20 '17 at 15:18

gold_cy · Answer 1 · 2017-04-20T17:02:02.250

5

Here is another way of doing it:

files = []

for _, _, f in os.walk('directory'):
    files.append(f)

sorted(files,key=lambda x: ext_list.index(*[os.path.basename(x).split('.',1)[-1]]))

['buzz.bb', 'foo.cc', 'fizz.aa']

Edit: My output doesn't have dd since I didn't make a file for it in my local test dir. It will work regardless.

edited Apr 20 '17 at 17:02

answered Apr 20 '17 at 15:34

gold_cy

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2

@bernie what is this sorcery?! – gold_cy Apr 20 '17 at 15:43
`files.append(files)` ? did you mean `files.append(file)` ? it's like you re appending the list to itself? also, i get an error stating that one extension that i defined does not exist – uniXVanXcel Apr 20 '17 at 16:58
1

@Pythus it was a typo, fixed – gold_cy Apr 20 '17 at 17:02

Brian · Accepted Answer · 2017-04-20T18:32:14.397

3

You can use sorted() with a custom key:

import os

my_custom_keymap = {".aa":2, ".bb":3, ".cc":0, ".dd":1}
def mycompare(f):
    return my_custom_keymap[os.path.splitext(f)[1]]

files = ["alfred.bb", "butters.dd", "charlie.cc", "derkins.aa"]

print(sorted(files, key=mycompare))

The above uses the mycompare function as a custom key compare. In this case, it extracts the extension, and the looks up the extension in the my_custom_keymap dictionary.

A very similar way (but closer to your example) could use a list as the map:

import os

my_custom_keymap = [".cc", ".dd", ".aa", ".bb"]
def mycompare(f):
    return my_custom_keymap.index(os.path.splitext(f)[1])

files = ["alfred.bb", "butters.dd", "charlie.cc", "derkins.aa"]

print(sorted(files, key=mycompare))

edited Apr 20 '17 at 18:32

answered Apr 20 '17 at 15:25

Brian

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14
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thank you!. your extension is only a single character though, does it matter if mine are 2 or 3? – uniXVanXcel Apr 20 '17 at 15:43
`my_custom_keymap = {key:value for value, key in enumerate(ext_list)}` `key=lambda f: my_custom_keymap[os.path.splitext(f)[1]]` – Harvey Apr 20 '17 at 15:50
1

@Pythus - nope, the extensions can be any length, which you've probably figured out by now. – Brian Apr 20 '17 at 18:30

score 2 · Answer 3 · answered Apr 20 '17 at 15:28

import os
# List you should get once:
file_list_name =['mickey.aa','mickey.dd','mickey_B.cc','mickey.bb']
ext_list = [ '.bb', '.cc' , '.dd' , '.aa' ]

order_list =[]
for ext in ext_list:
    for file in file_list_name:
        extension = os.path.splitext(file)[1]
        if extension == ext:
            order_list.append(file)

order_list is what you are looking for. Otherwise you can use the command sorted() with key attribute. Just look for it on SO!

score 1 · Answer 4 · answered Apr 20 '17 at 15:47

Using sorted with a custom key is probably best, but here's another method where you store the filenames in lists based on their extension. Then put those lists together based on your custom order.

def get_sorted_list_of_files(dirname, extensions):
    extension_map = collections.defaultdict(list)
    for _, _, files in os.walk(dirname):
        for filename in files:
            extension = os.path.splitext(filename)[1]
            extension_map[extension].append(filename)
    pprint.pprint(extension_map)
    sorted_list = []
    for extension in extensions:
        sorted_list.extend(extension_map[extension])
    pprint.pprint(extensions)
    pprint.pprint(sorted_list)
    return sorted_list

How can I sort given a specific order that I provide

4 Answers4