- 1 year ago
Check for exclusive file lock in python 3
To check for an exclusive file lock in Python 3, you can use the fcntl
module. Here's an example:
pythonimport fcntl
import os
filename = 'myfile.txt'
# Open the file in read-only mode
with open(filename, 'r') as file:
# Get the file descriptor
fd = file.fileno()
try:
# Check if the file is locked
fcntl.flock(fd, fcntl.LOCK_EX | fcntl.LOCK_NB)
# If the file is not locked, do something
print('File is not locked')
except OSError as e:
# If the file is locked, handle the exception
if e.errno == errno.EAGAIN:
print('File is locked')
else:
raise
In this example, we open the file in read-only mode and get its file descriptor using the fileno()
method. We then use the fcntl.flock()
function to try to obtain an exclusive lock on the file. The fcntl.LOCK_EX
flag indicates that we want an exclusive lock, and the fcntl.LOCK_NB
flag indicates that we want to try to obtain the lock non-blocking.
If the file is not locked, the fcntl.flock()
call will succeed and we can proceed with whatever we want to do with the file. If the file is locked, an OSError
exception will be raised with an errno
attribute of errno.EAGAIN
, indicating that the lock could not be obtained.
Note that this approach only works for file locks obtained with fcntl
. If the file is locked by another process or with a different method (e.g., using the msvcrt.locking()
function on Windows), this method will not detect the lock.