PySide: How can I pass additional arguments to a slot connected to QProcess finished signal in addition to the exitCode it sends?

Question

QProcess's finished signal returns exitCode as a parameter. I am trying to create a lambda function to connect this signal, but I can't figure out how to send additional arguments to it:

    b=2
    process.finished.connect(lambda a=a:self.onFinish(a))

def onFinish(self,exitCode,a):
   #do something

The error I get is:

TypeError: onFinish() takes exactly 3 arguments (2 given)

I was hoping that the exitStatus would automatically get propagated to the lambda function, but it doesn't seem to.

The above code does not seem to work.