python - specifically handle file exists exception

Question

I have come across examples in this forum where a specific error around files and directories is handled by testing the errno value in OSError (or

Answer 1

Here's an example of dealing with a race condition when trying to atomically overwrite an existing symlink:

# os.symlink requires that the target does NOT exist.
# Avoid race condition of file creation between mktemp and symlink:
while True:
    temp_pathname = tempfile.mktemp()
    try:
        os.symlink(target, temp_pathname)
        break  # Success, exit loop
    except FileExistsError:
        time.sleep(0.001)  # Prevent high load in pathological conditions
    except:
        raise
os.replace(temp_pathname, link_name)