[Urwid] attribute error encountered while using a render function from Frame class.

[SHAIKH TAUSEEF HUSSAIN]

Uwid code below creates a layout and displays some text in the layout. Next
the layout is displayed on the console screen using raw display module from
urwid library. (More info on my complete project can be gleaned from
questions at [widget advice for a console project](
http://stackoverflow.com/questions/17846930/required-widgets-for-displaying-a-1d-console-application)
and [urwid for a console project](
http://stackoverflow.com/questions/17381319/using-urwid-to-create-a-2d-console-application).
My skype help request being [here](
http://stackoverflow.com/questions/17846113/widget-to-choose-for-1d-urwid-application).)
However running the code fails as an AttributeError is raised as described
below. On looking at source code for urwid at
/usr/lib64/python2.7/site-packages/urwid I see that both main_loop.py and
curses_display.py have a draw_screen function with different arguments :
main_loop.py -> def draw_screen(self):

curses_display.py > def draw_screen(self, (cols, rows), r ):

Do I have to specify which one to use by something like **import
draw_screen from specificFile** command ? Or is there anything
fundamentally wrong I am looking at the canvas concept ? I can also see
that the frame class (**class Frame(BoxWidget):** ) in the file
/usr/lib64/python2.7/site-packages/urwid/**container.py** has a render
function (**def render(self, size, focus=False):**)


Error on running code is :
`
Traceback (most recent call last):
File "./yamlUrwidUIPhase6.py", line 104, in <module>
main()
File "./yamlUrwidUIPhase6.py", line 98, in main
form.main()
File "./yamlUrwidUIPhase6.py", line 51, in main
self.loop.run()
File "/usr/lib64/python2.7/site-packages/urwid/main_loop.py", line
274, in run
self.screen.run_wrapper(self._run)
File "/usr/lib64/python2.7/site-packages/urwid/raw_display.py", line
237, in run_wrapper
return fn()
File "/usr/lib64/python2.7/site-packages/urwid/main_loop.py", line
285, in _run
self.draw_screen()
File "/usr/lib64/python2.7/site-packages/urwid/main_loop.py", line
508, in draw_screen
canvas = self._topmost_widget.render(self.screen_size, focus=True)
AttributeError: 'NoneType' object has no attribute 'render'
`

The code :

import sys
sys.path.append('./lib')
import os
from pprint import pprint
import random
import urwid
ui=urwid.raw_display.Screen()


class FormDisplay(object):

def __init__(self):
global ui
self.ui = ui
self.palette = self.ui.register_palette([
('Field', 'dark green, bold', 'black'), # information
fields, Search: etc.
('Info', 'dark green', 'black'), # information in fields
('Bg', 'black', 'black'), # screen background
('InfoFooterText', 'white', 'dark blue'), # footer text
('InfoFooterHotkey', 'dark cyan, bold', 'dark blue'), #
hotkeys in footer text
('InfoFooter', 'black', 'dark blue'), # footer background
('InfoHeaderText', 'white, bold', 'dark blue'), # header
text
('InfoHeader', 'black', 'dark blue'), # header background
('BigText', RandomColor(), 'black'), # main menu banner text
('GeneralInfo', 'brown', 'black'), # main menu text
('LastModifiedField', 'dark cyan, bold', 'black'), # Last
modified:
('LastModifiedDate', 'dark cyan', 'black'), # info in Last
modified:
('PopupMessageText', 'black', 'dark cyan'), # popup message
text
('PopupMessageBg', 'black', 'dark cyan'), # popup message
background
('SearchBoxHeaderText', 'light gray, bold', 'dark cyan'), #
field names in the search box
('SearchBoxHeaderBg', 'black', 'dark cyan'), # field name
background in the search box
('OnFocusBg', 'white', 'dark magenta') # background when a
widget is focused
])
urwid.set_encoding('utf8')

def main(self):
global ui
#self.view = ui.run_wrapper(formLayout)
self.ui.start()
self.view = formLayout()

self.loop = urwid.MainLoop(self.view, self.palette,
unhandled_input=self.unhandled_input)
self.loop.run()

def unhandled_input(self, key):
if key == 'f8':
quit()
return


def formLayout():
global ui
text1 = urwid.Text("Urwid 3DS Application program - F8 exits.")
text2 = urwid.Text("One mission accomplished")

textH = urwid.Text("topmost Pile text")
cols = urwid.Columns([text1,text2])
pile = urwid.Pile([textH,cols])
fill = urwid.Filler(pile)

textT = urwid.Text("Display")

textSH = urwid.Text("Pile text in Frame")
textF = urwid.Text("Good progress !")

frame =
urwid.Frame(fill,header=urwid.Pile([textT,textSH]),footer=textF)
dim = ui.get_cols_rows()
#ui is treated as global handle for all functions, either belonging
#to any class or standalone functions such as formLayout
#need to check if screen has been started
if not ui._started:
print("Screen has not been started, so no use of rendering.Thus
return :-( ")
return

ui.draw_screen(dim, frame.render(dim, True))
return

def RandomColor():
'''Pick a random color for the main menu text'''
listOfColors = ['dark red', 'dark green', 'brown', 'dark blue',
'dark magenta', 'dark cyan', 'light gray',
'dark gray', 'light red', 'light green', 'yellow',
'light blue', 'light magenta', 'light cyan',
'default']
color = listOfColors[random.randint(0, 14)]
return color

def main():
form = FormDisplay()
form.main()

########################################
##### MAIN ENTRY POINT
########################################
if __name__ == '__main__':
main()


I don't want to change the function formLayout as I intend to add more to
this basic code framework, where in another function will be added that
repeatedly calls formLayout to keep updating the screen based on reading
values from a yml file. I already have a separate code that deals with
reading the yaml file and extracting ordered dictionaries out it. After
figuring out how to get basic urwid console working, I can move on to
integrating both to create my final application.

regards
Tauseef

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1. Re: creating a 2D console application with urwid. (Ian Ward)
----------------------------------------------------------------------
Message: 1
Date: Wed, 10 Jul 2013 11:53:23 -0400
From: Ian Ward <ian at excess.org>
Subject: Re: [Urwid] creating a 2D console application with urwid.
To: Urwid General Discussion <urwid at lists.excess.org>
<
CAA3rUNcHR7-13jtRUQ3SuSEEKhp5tjGA1eu7SeyQHbqA+bFJ9Q at mail.gmail.com>
Content-Type: text/plain; charset=ISO-8859-1
On Sat, Jun 29, 2013 at 11:19 AM, SHAIKH TAUSEEF HUSSAIN

hi
I am a new user to urwid and python and
I am trying to build a 2D urwid application
that takes as input a yml schema file (attached )
and displays it on the screen as it appears
at this webpage : http://www.technion3ds.org/apply/
From the list of applications at urwid's site
I looked at two of them : d0Xbase and jsonwidget.
http://sourceforge.net/projects/d0xbase/
http://blog.robla.net/2010/jsonwidget-python/
What i need is the 2D functionality from d0xbase
and the input file handling facility from jsonwidget.
however jsonwidget has a jsonfile editor.
Could you suggest me the relevant links/sources/files/literature
I should look at if I intend to resuse the ideas from above applications
and build the application that i want to ?
your help will be highly appreciated.

Hello Tauseef,
I can only suggest reading the source of Urwid programs that are
similar to what you want. There are a number of links to applications
using Urwid on the web site.
When you have more specific questions I'm happy to help with those.
The IRC channel is often good for that too.
Ian
------------------------------
_______________________________________________
Urwid mailing list
Urwid at lists.excess.org
http://lists.excess.org/mailman/listinfo/urwid
End of Urwid Digest, Vol 92, Issue 1
************************************

[Ian Ward]

On Sun, Jul 28, 2013 at 11:35 AM, SHAIKH TAUSEEF HUSSAIN

Post by SHAIKH TAUSEEF HUSSAIN
Uwid code below creates a layout and displays some text in the layout. Next
the layout is displayed on the console screen using raw display module from
urwid library. (More info on my complete project can be gleaned from
questions at [widget advice for a console
project](http://stackoverflow.com/questions/17846930/required-widgets-for-displaying-a-1d-console-application)
and [urwid for a console
project](http://stackoverflow.com/questions/17381319/using-urwid-to-create-a-2d-console-application).
My skype help request being
[here](http://stackoverflow.com/questions/17846113/widget-to-choose-for-1d-urwid-application).)
However running the code fails as an AttributeError is raised as described
below. On looking at source code for urwid at
/usr/lib64/python2.7/site-packages/urwid I see that both main_loop.py and
Do I have to specify which one to use by something like **import draw_screen
from specificFile** command ? Or is there anything fundamentally wrong I am
looking at the canvas concept ? I can also see that the frame class (**class
Frame(BoxWidget):** ) in the file
/usr/lib64/python2.7/site-packages/urwid/**container.py** has a render
function (**def render(self, size, focus=False):**)

These two methods don't conflict in any way, and importing doesn't
affect which is used.

MainLoop is a thing that wants to be responsible for handling user
input and redrawing the screen when necessary. Its draw_screen()
method lets you force a screen redraw in cases where the MainLoop
can't tell that it needs to redraw the screen. Since MainLoop has a
screen and widgets to draw its draw_screen() method has no additional
parameters.

raw_display.Screen.draw_screen() takes a rendered canvas and actually
redraws all or part of the whole screen, so it takes the size and
canvas to draw.

Post by SHAIKH TAUSEEF HUSSAIN
File "./yamlUrwidUIPhase6.py", line 104, in <module>
main()
File "./yamlUrwidUIPhase6.py", line 98, in main
form.main()
File "./yamlUrwidUIPhase6.py", line 51, in main
self.loop.run()
File "/usr/lib64/python2.7/site-packages/urwid/main_loop.py", line
274, in run
self.screen.run_wrapper(self._run)
File "/usr/lib64/python2.7/site-packages/urwid/raw_display.py", line
237, in run_wrapper
return fn()
File "/usr/lib64/python2.7/site-packages/urwid/main_loop.py", line
285, in _run
self.draw_screen()
File "/usr/lib64/python2.7/site-packages/urwid/main_loop.py", line
508, in draw_screen
canvas = self._topmost_widget.render(self.screen_size, focus=True)
AttributeError: 'NoneType' object has no attribute 'render'

This Python error says that self._topmost_widget is None. We can see
that that value is the loop.widget set in the MainLoop initializer.
Following your code here is where you pass in the widget for the

Post by SHAIKH TAUSEEF HUSSAIN
global ui
#self.view = ui.run_wrapper(formLayout)
self.ui.start()
self.view = formLayout()
self.loop = urwid.MainLoop(self.view, self.palette,
unhandled_input=self.unhandled_input)

so, self.view here is None too. So it looks like formLayout() is not
returning a widget.

Hope this helps.

Ian