testdir.py

import os.path

from base64 import b64decode

from PyQt4.QtCore import QDir

HOST_DB = os.path.expanduser('~/.dropbox/host.db')


def get_dropbox_dir():
	with open(HOST_DB, 'rb') as hdb:
		hdb.readline()
		b64_path = hdb.readline()
		return b64decode(b64_path).decode('utf-8')


def dropboxify_dir(dir_to_test):
	print()
	print(dir_to_test.path())
	dropbox_root = QDir(get_dropbox_dir())
	canonical_root = QDir(dropbox_root.canonicalPath())
	
	relative = canonical_root.relativeFilePath(dir_to_test.canonicalPath())
	
	print(relative)
	if relative.startswith('..'):
		print('not below Dropbox')
		return None
	else:
		ret = QDir(dropbox_root)  #root saved in dropbox settings
		ret.cd(relative)
		print(ret.path())
		return ret

print(get_dropbox_dir())
dropboxify_dir(QDir(os.path.expanduser('~/Dropbox/Public')))
dropboxify_dir(QDir('/opt/Dropbox-Files/Dropbox/Dev'))
dropboxify_dir(QDir('/var/'))

output:

/opt/Dropbox-Files/Dropbox

/home/phil/Dropbox/Public
Public
/opt/Dropbox-Files/Dropbox/Public

/opt/Dropbox-Files/Dropbox/Dev
Dev
/opt/Dropbox-Files/Dropbox/Dev

/var
../../../var
not below Dropbox