python - 使用 QFileSystemWatcher 获取已更改文件的路径？

Question

摘自 How do I watch a file for changes? 中的片段:

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

我假设处理程序的参数 path 是已更改的文件的路径( http://doc.qt.io/qt-4.8/qfilesystemwatcher.html 并没有真正说明应该预期的内容 表示“_{fileChanged ...当指定路径处的文件被修改、重命名或从磁盘中删除时，会发出信号。}” )。但是，然后我运行以下示例(ubuntu 14.04，python 2.7.6，对应 py-qt4):

import sys, os
from PyQt4 import QtGui, QtCore
from PyQt4.QtCore import SIGNAL
from PyQt4 import Qt

mydir = os.path.dirname( os.path.realpath(__file__) )
myfile = os.path.join( mydir, "file.dat" )
print("myfile", myfile)

with open(myfile,"a+") as f:
  f.write("line 1\n")

class MyWindow(QtGui.QWidget):
  def __init__(self):
    global myfile
    QtGui.QWidget.__init__(self)
    self.button = QtGui.QPushButton('Test', self)
    self.button.clicked.connect(self.handleButton)
    layout = QtGui.QVBoxLayout(self)
    layout.addWidget(self.button)
    self.fs_watcher = QtCore.QFileSystemWatcher( [myfile] )
    self.fs_watcher.connect(self.fs_watcher, QtCore.SIGNAL('fileChanged(const QString &)'), self.file_changed) # or just 'fileChanged(QString)'
  def handleButton(self):
    print ('Hello World')
  @QtCore.pyqtSlot(str) #
  def file_changed(path):
    print('File Changed!!!' + str(path)) #

if __name__ == '__main__':
  app = QtGui.QApplication(sys.argv)
  window = MyWindow()
  # try to trigger file change here:
  with open(myfile,"a+") as f:
    f.write("line 2\n")
  window.show()
  sys.exit(app.exec_())

...它输出:

...
File Changed!!!<__main__.MyWindow object at 0xb5432b24>
...

所以，该参数似乎没有接收更改文件的路径，而是接收对包含类的引用？!

那么如何获取已更改文件的路径？

Answer 1

如果要成为 MyWindow 的方法，file_changed 插槽需要一个 self 参数:

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