[PyQt] QWidget call other __init__ methods, but why?

[Phil Thompson]

On 28 Jun 2016, at 4:52 pm, Barry Scott <barry at barrys-emacs.org> wrote:
> 
> Here we have a class that I use in my app. I just fixed a bug
> where wbTrackedModeless.__init__ was called twice as proved
> by using traceback.print_stack().
> 
> class WbTrackedModelessQWidget(QtWidgets.QWidget, WbTrackedModeless):
>    def __init__( self ):
>        QtWidgets.QWidget.__init__( self, None ) # line 50
>    def closeEvent( self, event ):
>        WbTrackedModeless.closeEvent( self, event )
> 
>        super().closeEvent( event )
> 
> From the definition it looks like wbTrackedModeless.__init__ is 
> not called.
> 
> However here is the stack:
> 
>  File "wb_scm_main.py", line 21, in <module>
>    sys.exit( wb_main.main( wb_scm_app.WbScmApp, sys.argv ) )
>  File "/Users/barry/wc/git/scm-workbench/Source/Common/wb_main.py", line 52, in main
>    rc = app.exec_()
>  File "/Users/barry/wc/git/scm-workbench/Source/Git/wb_git_ui_actions.py", line 172, in treeTableActionGitLogHistory
>    self.main_window.callTreeOrTableFunction( self.treeActionGitLogHistory, self.tableActionGitLogHistory )
>  File "/Users/barry/wc/git/scm-workbench/Source/Scm/wb_scm_main_window.py", line 617, in callTreeOrTableFunction
>    return fn_tree()
>  File "/Users/barry/wc/git/scm-workbench/Source/Git/wb_git_ui_actions.py", line 347, in treeActionGitLogHistory
>    self.main_window.getQIcon( 'wb.png' ) )
>  File "/Users/barry/wc/git/scm-workbench/Source/Git/wb_git_log_history.py", line 162, in __init__
>    super().__init__()
>  File "/Users/barry/wc/git/scm-workbench/Source/Common/wb_tracked_qwidget.py", line 50, in __init__
>    QtWidgets.QWidget.__init__( self, None )
>  File "/Users/barry/wc/git/scm-workbench/Source/Common/wb_tracked_qwidget.py", line 29, in __init__
>    self.__trackWidget()
>  File "/Users/barry/wc/git/scm-workbench/Source/Common/wb_tracked_qwidget.py", line 34, in __trackWidget
>    traceback.print_stack()
> 
> This shows that QtWidgets.QWidget.__init__( self, None ) called WbTrackedModeless.__init__()
> (__trackWidget is first line of __init__ at line 29).
> 
> I guess Phil this is a question for you.
> 
> Why does PyQt call __init__ if there is multiple inheritance? Is this a bug in PyQt?

See...

http://pyqt.sourceforge.net/Docs/PyQt5/multiinheritance.html

Phil