>>> os.mkdir('dir')
>>> os.access('dir', os.W_OK)
True
>>> os.access('nonexistent', os.W_OK)
False
>>> open('dir/bar')
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
FileNotFoundError: [Errno 2] No such file or directory: 'dir/bar'
>>> open('nonexistent/bar')
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
FileNotFoundError: [Errno 2] No such file or directory: 'nonexistent/bar'