Check if directory 'B' is inside directory 'A'

Question

I am developing a script that checks the last access date of each file within every tree of a chosen directory. Files over X days without access will be moved to another directory. As a precaution, I need it detected if the destination directory is inside the source directory. If so, the script will ask for a destination directory other than within the source directory.

This is the part where the destination directory is requested:

msg_error = '[ERRO] Diretorio invalido, tente novamente:\n'
pasta_destino = str(input('Insira o diretorio de destino\n'))
while not path.isdir(pasta_destino):
    pasta_destino = str(input(msg_error))

I’ve been trying to check this out for a long time, and I’ve tried everything. I’ve only been learning python for a week and something closer to the check I was able to assemble was this:

if path.exists(pasta_destino in pasta_origem):
     print('Escolha outro diretório que não dentro do diretório de origem.\n')

Unfortunately it does not work, returns 'True' independent of the inserted paths.

I’m sure this is a simple check, can you help me? Thank you very much.

Answer 1

Use Pathlib:

from pathlib import Path
def is_sub(root, directory):
    p = Path(root)
    return True if list(p.glob(directory)) else False

Testing on Linux (ipython terminal)

mkdir ~/teste1
cd ~/teste1
mkdir dir1

is_sub('.','dir1')
True

is_sub('.','dir2')
False

is_sub('/home/sidon','Downloads')
True

Test on Windows:

is_sub('/','users')
True

Answer 2

def subdir(pai, filho):
    return os.path.abspath(filho).startswith(os.path.abspath(pai) + os.path.sep)

Note that this function does not check whether directories exist, only if one is contained in the other, however, it would be easy to modify and add further this check.