Print the top 20 folder that are using more space.

diskindex.py

#!/usr/bin/env python3
# Copyright 2017 Daniel Hilst Selli
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#    http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.

import subprocess

def yieldindex(lines):
    for line in lines:
        siz, path = line.split(maxsplit=1)
        yield siz, path.split('/')[1:]

def createindex(foldr):
    g = (line.rstrip() for line in subprocess.Popen(['find', foldr, '-xdev', '-printf', '%k %p\\n'],
					stdout=subprocess.PIPE, universal_newlines=True).stdout.readlines())
    yield from yieldindex(g)
            
def readindex(index):
    with open(index) as f:
        yield from yieldindex(f.readlines())

def genindex(indexgen):
    index = {}
    for siz, path in indexgen:
        for folder in ('/'.join(path[:n]) for n in range(1, len(path)+1)):
            index[folder] = int(siz) if not folder in index else index[folder] + int(siz)
    return index

def printindex(idx, max_=20):
    for e,(k,v) in enumerate(sorted(idx.items(), key=lambda x: x[1], reverse=True)):
        print(v, k)
        if e > max_:
            break

if __name__ == '__main__':
    import sys
    try:
        printindex(genindex(readindex(sys.argv[1])))
    except IsADirectoryError:
        printindex(genindex(createindex(sys.argv[1])))
    except IndexError:
        print('Usage: diskindex.py index.txt\n'
              'Index can be constructed with `find <MOUNT_POINT> -xdev -print "%k %p\\n" > diskindex.txt`.\n'
              'or\n'
              'diskindex.py <DIRECTORY>\n'
              'In this case the index is created automatically\n')