Kivy: FileChooser virtual filesystem

virtualfs.py

import kivy
kivy.require('1.9.0')

from kivy.app import App
from kivy.uix.filechooser import FileChooser, FileSystemAbstract, FileChooserIconLayout

virtual_files = {
    'a': {
        'size': 20,
        'files': {
            'a1': {
                'size': 30
            }
        }
    },
    'b': {
        'size': 100
    },
    'c': {
        'size': 50,
        'files': {'c1': {
                      'size': 10
                  },
                  'c2': {
                    'size': 50,
                      'files': {
                          'c21': {
                              'size': 10000
                          }
                      }
                  }
        }
    }
}

class FileSystemVirtual(FileSystemAbstract):
    def __init__(self, files):
        self.files = files
    
    def _collapse(self, nameparts):
        while '.' in nameparts:
            nameparts.remove('.')
        
        while '' in nameparts:
            nameparts.remove('')
        
        while '..' in nameparts:
            i = nameparts.index('..')
            nameparts = nameparts[:i - 1] + nameparts[i + 1:]
        
        return nameparts
    
    def _getentry(self, name):
        parts = name.strip('/').split('/')
        parts = self._collapse(parts)
        target = {'files': self.files, 'size': 0}
        while parts:
            nextpart = parts[0]
            parts = parts[1:]
            target = target['files'][nextpart]
        return target
    
    def listdir(self, fn):
        target = self._getentry(fn)
        return target['files'].keys()
    
    def getsize(self, fn):
        target = self._getentry(fn)
        return target['size']
    
    def is_hidden(self, fn):
        return False
    
    def is_dir(self, fn):
        target = self._getentry(fn)
        return 'files' in target

class TestApp(App):
    def build(self):
        fc = FileChooser(file_system=FileSystemVirtual(virtual_files), path='/')
        fc.add_widget(FileChooserIconLayout())
        return fc

if __name__ == '__main__':
    TestApp().run()