I met an issue when using multi inheritance with PyQt, the Programe 1# source code as below:
#!python3
import sys;
from PyQt5.QtWidgets import *;
from PyQt5.QtGui import *;
from PyQt5.QtCore import *;
class WP_Widget(QWidget):
def __init__(self):
print("WP_Widget init");
super().__init__();
class WP_Line(QLineEdit):
def __init__(self, text='',*args, **kargs):
super().__init__();
self.setText(text);
class Widget_C(WP_Widget, WP_Line):
#class Widget_C(WP_Line, WP_Widget):
def __init__(self):
print('Widget_C self = ', self)
super().__init__();
class App(QWidget):
def __init__(self):
super().__init__();
fname = Widget_C();
self.left = 100
self.top = 100
self.width = 100
self.height = 100
self.show();
if __name__ == '__main__':
app = QApplication(sys.argv)
ex = App()
sys.exit(app.exec_())
When execute, it will show the error as:
AttributeError: 'Widget_C' object has no attribute 'setText'
If change Widget_C definition
from
class Widget_C(WP_Widget, WP_Line):
to
class Widget_C(WP_Line, WP_Widget):
It will run successfully.
I guess it will be related to MRO in Python3, so I write another program 2# to simulate the state:
#!python3
class QWidget():
def __init__(self):
print("Base QWidget init.");
class QLineEdit(QWidget):
def __init__(self):
print('LineEdit init');
super().__init__();
def setText(self, text):
print('setText called');
class WP_Widget(QWidget):
def __init__(self):
print('WP_Widget Init');
super().__init__()
class WP_Line(QLineEdit):
def __init__(self, text='',*args, **kargs):
print('WP_Line init');
super().__init__();
self.setText(text)
class Widget_C(WP_Widget, WP_Line):
#class Widget_C(WP_Line, WP_Widget):
def __init__(self):
super().__init__()
c_test = Widget_C()
But no matter which inheriting sequence of Wiget_C,
class Widget_C(WP_Line, WP_Widget):
or
class Widget_C(WP_Widget, WP_Line):
both of them will run normally.
So could anyone help:
- Explain why program 1# fails when defined as
class Widget_C(WP_Widget, WP_Line):, MRO is just my guess. - Why program 2# can be run normally in both condition ?
- Help modify program 2# to reproduce the state of program 1# .
Python and order of methods in multiple inheritance explains something about MRO, it related to my question, but not exactly the answer. If inheriting order is the same, my program 1# and program 2 should not have different results, so the key point is why program 1# and program 2 have different phenomenon.
