How do I watch a file for changes?

Question

I have a log file being written by another process which I want to watch for changes. Each time a change occurs I\'d like to read the new data in to do some processing on it

Answer 1

If you want a multiplatform solution, then check QFileSystemWatcher. Here an example code (not sanitized):

from PyQt4 import QtCore

@QtCore.pyqtSlot(str)
def directory_changed(path):
    print('Directory Changed!!!')

@QtCore.pyqtSlot(str)
def file_changed(path):
    print('File Changed!!!')

fs_watcher = QtCore.QFileSystemWatcher(['/path/to/files_1', '/path/to/files_2', '/path/to/files_3'])

fs_watcher.connect(fs_watcher, QtCore.SIGNAL('directoryChanged(QString)'), directory_changed)
fs_watcher.connect(fs_watcher, QtCore.SIGNAL('fileChanged(QString)'), file_changed)