Pyqt5, Signal有分Unbound and Bound Signals

A bound signal has connect(), disconnect() and emit() methods that implement the associated functionality.

New signals should only be defined in sub-classes of QObject.They must be part of the class definition and cannot be dynamically added as class attributes after the class has been defined.
==>
在PyQt5中,
class QTd(QtCore.QThread):

    msig = QtCore.pyqtSignal(str, str)

    psig = QtCore.pyqtSignal(QtWidgets.QPushButton, bool)

    def __init__(self, fi, table, pbutton, sbox, parent = None):

        super().__init__(parent)

        self.fi = fi

        self.table = table

        self.pbutton = pbutton

        self.sbox = sbox

        self.msig.connect(self.showmbox)

        self.psig.connect(self.setpb)

==>

msig和psig是class variable, 

self.fi, self.table, self.pbutton, self.sbox是instance variable,

在此msig和psig是bound signal, 

(<class 'PyQt5.QtCore.pyqtBoundSignal'>)

如果宣告在class QTd的__init__底下，變成

self.msig = QtCore.pyqtSignal(str, str)

self.psig = QtCore.pyqtSignal(QtWidgets.QPushButton, bool)

那麼self.msig和self.psig就變成unbound signal, 

(<class 'PyQt5.QtCore.pyqtSignal'>)

unbound signal就沒有connect() method了。

詳參：

https://stackoverflow.com/questions/17578428/pyqt5-signals-and-slots-qobject-has-no-attribute-error