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

SHAIKH TAUSEEF HUSSAIN tauseef at nitc.ac.in
Sun Jul 28 11:35:51 EDT 2013

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](
and [urwid for a console project](
My skype help request being [here](
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>
      File "./yamlUrwidUIPhase6.py", line 98, in main
      File "./yamlUrwidUIPhase6.py", line 51, in main
      File "/usr/lib64/python2.7/site-packages/urwid/main_loop.py", line
274, in 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
      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
    import os
    from pprint import pprint
    import random
    import urwid

    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
                ('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
                ('LastModifiedDate', 'dark cyan', 'black'), # info in Last
                ('PopupMessageText', 'black', 'dark cyan'), # popup message
                ('PopupMessageBg', 'black', 'dark cyan'), # popup message
                ('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

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

            self.loop = urwid.MainLoop(self.view, self.palette,

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

    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 =
        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 :-( ")

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

    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',
        color = listOfColors[random.randint(0, 14)]
        return color

    def main():
        form = FormDisplay()

    if __name__ == '__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.


On Wed, Jul 10, 2013 at 12:00 PM, <urwid-request at lists.excess.org> wrote:

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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>
> Message-ID:
>         <
> 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
> <tauseef at nitc.ac.in> wrote:
> > 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
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Kind Regards
Tauseef Hussain
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