[Tutor] How to access a method defined in one class from another class (which is a thread) in Python3?

[Prasad, Ramit]

SM wrote:
> 
> I am defining multiple classes (some of them are threads)
> I have been writing Python programs for a few months, but never faced this issue so far unless I am
> doing something different inadvertently. The only difference I see is that I am calling the methods
> belonging to other classes, from a class which is also a thread.
>  I see the following error:
> 
> AttributeError: 'Ui_MainWindow' object has no attribute 'textEdit_fwcmdlineoutput'
> Code Snippets:
> 
> class Ui_MainWindow(object):
>     [snip]
> 
>     def setStdoutToTextEditWindowFw(self):
>           self.textEdit_fwcmdlineoutput.setText( sys.stdout.getvalue() )
>           sys.stdout = self.oldstdout
> Calling the above method from within the class works fine. But I am calling it from another class as
> below:
> 
> class bcThread(threading.Thread):
>     def __init__(self, cmd):
>         threading.Thread.__init__(self)
>         self.cmd = cmd
>     def run(self):
>         [snip]
>         Ui_MainWindow.setStdoutToTextEditWindowFw(Ui_MainWindow)
> The highlighted line gives the following error :
> 
> Exception in thread Thread-1:
> Traceback (most recent call last):
>   File "/usr/lib/python3.2/threading.py", line 740, in _bootstrap_inner
>     self.run()
>   File "bc_reports_tab.py", line 1299, in run
>     Ui_MainWindow.setStdoutToTextEditWindowFw(Ui_MainWindow)
>   File "bc_reports_tab.py", line 465, in setStdoutToTextEditWindowFw
>     self.textEdit_fwcmdlineoutput.setText( sys.stdout.getvalue() )
> AttributeError: type object 'Ui_MainWindow' has no attribute 'textEdit_fwcmdlineoutput'
> I also tried many different ways of calling the method. The highlighted line is one of them. Another
> one I tried is here where I create an instance, which also gives the same error:
> 
> x = Ui_MainWindow()
> x.setStdoutToTextEditWindowFw()
> I see the same error.

I do not think that actually gave you the same error.
Most likely it gave you a *similar* error. See the below.

>>> o = object()
>>> o.blah # on instance object, not class object
AttributeError: 'object' object has no attribute 'blah'

>>> object.blah # on class object, not instance object
AttributeError: type object 'object' has no attribute 'blah'


If you got the top error from the snippet where you instantiate 
an instance of Ui_MainWindow then I believe some function must 
create the textEdit_fwcmdlineoutput attribute and that needs 
to be called first. I would have imagined this creation should 
occur on __init__ but obviously it must be somewhere else. 
You will need to call that section of code. It should be in 
the Ui_MainWindow class and look something like:

self.textEdit_fwcmdlineoutput = <create TextEdit object here>

> Can someone guide me as to what is the correct way to do something like this?
> 
> Thanks in advance.
> -SM
> 



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