On Python ≥ 3.5, use
from pathlib import Path
For older versions of Python, I see two answers with good qualities, each with a small flaw, so I will give my take on it:
os.path.exists, and consider
os.makedirs for the creation.
if not os.path.exists(directory):
As noted in comments and elsewhere, there's a race condition – if the directory is created between the
os.path.exists and the
os.makedirs calls, the
os.makedirs will fail with an
OSError. Unfortunately, blanket-catching
OSError and continuing is not foolproof, as it will ignore a failure to create the directory due to other factors, such as insufficient permissions, full disk, etc.
One option would be to trap the
OSError and examine the embedded error code (see Is there a cross-platform way of getting information from Python’s OSError):
import os, errno
except OSError as e:
if e.errno != errno.EEXIST:
Alternatively, there could be a second
os.path.exists, but suppose another created the directory after the first check, then removed it before the second one – we could still be fooled.
Depending on the application, the danger of concurrent operations may be more or less than the danger posed by other factors such as file permissions. The developer would have to know more about the particular application being developed and its expected environment before choosing an implementation.
Modern versions of Python improve this code quite a bit, both by exposing
FileExistsError (in 3.3+)...
# directory already exists
...and by allowing a keyword argument to
exist_ok (in 3.2+).
os.makedirs("path/to/directory", exist_ok=True) # succeeds even if directory exists.
When you edit a QMainWindow you can right click the window and then choose "create menu bar".
Or are you talking about a "context menu" aka "right click menu"?