GUI Program Error

Hi, I'm using the "Learning to Program" GUI tutorial on
http://www.freenetpages.co.uk/hp/alan.gauld/
and am trying to write my first GUI. However, the code the tutorial
gives for starting by making a window:

import Tkinter

top = Tkinter.Tk()

dir(top)

Does not work. The Python interpreter does not complain about anything,
but the window the tutorial promises will apperar will not. I'm using
Python 2.4.2 and the Eric 3.7.0 IDE on Ubuntu 5.10. Anybody know what
to do?

-- /usr/bin/byte

Byte wrote:[color=blue]
> Hi, I'm using the "Learning to Program" GUI tutorial on
> http://www.freenetpages.co.uk/hp/alan.gauld/
> and am trying to write my first GUI. However, the code the tutorial
> gives for starting by making a window:
>
>
> import Tkinter
>
> top = Tkinter.Tk()
>
> dir(top)
>
> Does not work. The Python interpreter does not complain about anything,
> but the window the tutorial promises will apperar will not. I'm using
> Python 2.4.2 and the Eric 3.7.0 IDE on Ubuntu 5.10. Anybody know what
> to do?[/color]

You have to call top.mainloop() for it work. What is dir(), btw? Is it a
class for creating the application?

John Salerno wrote:
[color=blue]
> What is dir(), btw? Is it a
> class for creating the application?[/color]

Heh heh, how quickly I forget about built-ins. :) Try something like this:

import Tkinter as tk

root = tk.Tk()
label = tk.Label(root, text='Hello world!')
label.pack()
root.mainloop()

On 6/5/06, John Salerno <johnjsal@nospamgmail.com> wrote:[color=blue]
> What is dir(), btw? Is it a class for creating the application?[/color]

[Bernard] In your Python documentation, dir() is described in the
built-in functions (section 2.1) as well as the tutorial, in the
"Modules" section (chapter 6). Unless you were being sarcastic? ;-)

Bernard

Bernard Lebel wrote:
[color=blue]
> Unless you were being sarcastic? ;-)[/color]

Just temporarily dense. :)

Thanks, this works. Now, since the tutorial I was using is clearly
rubbish, any better ones? For a (relative) newbie please. Also, how do
I code a GUI Hello World program?

-- /usr/bin/byte

Byte wrote:[color=blue]
> Thanks, this works. Now, since the tutorial I was using is clearly
> rubbish, any better ones? For a (relative) newbie please. Also, how do
> I code a GUI Hello World program?
>
> -- /usr/bin/byte
>[/color]

Actually, that site is generally considered to be a pretty good place to
start for tutorials. I think maybe you didn't go far enough through the
"Tour of Some Common Widgets" section before you experienced problems
(i.e., you didn't get to pack() or mainloop(), etc.).

But I will agree with you that it is confusing when it says, following
the top = Tk() line, "Notice that a new blank window has appeared",
because as you noticed, nothing appears yet. My only guess is that this
is either a mistake, or the tutorial is a little old, because I think
Tkinter used to behave differently in the interactive prompt than it
does now.

Anyhow, I would stick with that site, but you might also try Fredrik's
tutorial: http://www.pythonware.com/library/tkinter/introduction/

It's a great little intro, but also a reference to the widgets, methods,
etc. I pretty much learned everything so far from that site (admittedly
I'm just as new as you are, but it's still a good site!) :)

Byte wrote:
[color=blue]
> Also, how do
> I code a GUI Hello World program?[/color]

P.S. The link I supplied begins with two versions of a Hello World app.

Byte wrote:[color=blue]
> Thanks, this works. Now, since the tutorial I was using is clearly
> rubbish, any better ones? For a (relative) newbie please. Also, how do
> I code a GUI Hello World program?
>
> -- /usr/bin/byte[/color]

How does John Salerno previous code NOT fit the bill?
[color=blue][color=green]
>> John Salerno wrote:
>> ...
>> import Tkinter as tk
>>
>> root = tk.Tk()
>> label = tk.Label(root, text='Hello world!')
>> label.pack()
>> root.mainloop()
>> ...[/color][/color]

I think you should get a copy of "an-introduction-to-tkinter" from
Fredrik Lundh and try out the different usage examples and experiment,
then post more specific questions (after searching this newsgroup since
many questions lie here already answered).

On Wed, 07 Jun 2006 17:38:39 GMT, John Salerno <johnjsal@NOSPAMgmail.com>
wrote:
[snip][color=blue]
> But I will agree with you that it is confusing when it says, following
> the top = Tk() line, "Notice that a new blank window has appeared",
> because as you noticed, nothing appears yet. My only guess is that this
> is either a mistake, or the tutorial is a little old, because I think
> Tkinter used to behave differently in the interactive prompt than it
> does now.[/color]

It may be a platform-specific issue: On Unix/Linux, a window *does* appear
when you instantiate Tk, at least with tcl/tk 8.3 and 8.4 (which is the
latest stable version AFAIK).
--
python -c "print ''.join([chr(154 - ord(c)) for c in
'U(17zX(%,5.zmz5(17l8(%,5.Z*(93-965$l7+-'])"

Eric Brunel wrote:
[color=blue]
> It may be a platform-specific issue: On Unix/Linux, a window *does* appear
> when you instantiate Tk, at least with tcl/tk 8.3 and 8.4 (which is the
> latest stable version AFAIK).[/color]

same on Windows, but it often appears *beneath* the window you're typing
into, so you have to look for it in the task bar.

this also relies on Python being able to keep the Tkinter event loop
going behind the scenes; different command-line implementations have
different limitations.

for example, on Windows, the event loop runs only when you're at an
empty Python prompt; as soon as you start typing the next command, the
interpreter switches over to "text input mode", and the event loop is
paused until you press return.

</F>

Fredrik Lundh wrote:[color=blue]
> Eric Brunel wrote:
>[color=green]
>> It may be a platform-specific issue: On Unix/Linux, a window *does*
>> appear when you instantiate Tk, at least with tcl/tk 8.3 and 8.4
>> (which is the latest stable version AFAIK).[/color]
>
> same on Windows, but it often appears *beneath* the window you're typing
> into, so you have to look for it in the task bar.
>
> this also relies on Python being able to keep the Tkinter event loop
> going behind the scenes; different command-line implementations have
> different limitations.
>
> for example, on Windows, the event loop runs only when you're at an
> empty Python prompt; as soon as you start typing the next command, the
> interpreter switches over to "text input mode", and the event loop is
> paused until you press return.
>
> </F>
>[/color]

I thought it might be something like that. A window doesn't appear for
me at all, but it may be because I haven't updated Tkinter since
installing Python, so maybe it's a little older.

John Salerno wrote:[color=blue]
> <Next from Fredrik Lundh>[color=green]
>> <Quoting Eric Brunel>[color=darkred]
>>> It may be a platform-specific issue: On Unix/Linux, a window *does*
>>> appear when you instantiate Tk, at least with tcl/tk 8.3 and 8.4
>>> (which is the latest stable version AFAIK).[/color][/color][/color]

Here you should have chimed in with your OS and Python versions.
[color=blue][color=green]
>> same on Windows, but it often appears *beneath* the window you're
>> typing into, so you have to look for it in the task bar.
>>
>> this also relies on Python being able to keep the Tkinter event loop
>> going behind the scenes; different command-line implementations have
>> different limitations.
>>
>> for example, on Windows, the event loop runs only when you're at an
>> empty Python prompt; as soon as you start typing the next command, the
>> interpreter switches over to "text input mode", and the event loop is
>> paused until you press return.[/color]
>
> I thought it might be something like that. A window doesn't appear for
> me at all, but it may be because I haven't updated Tkinter since
> installing Python, so maybe it's a little older.[/color]

When running on Windows 2000 (at least), with Python 2.3 or greater,
Idle now (by default) stays more separate from the process running the
user's code. As a result, debugging and namespaces are more stable, but
the users space doesn't have a display loop running. To help out in
cases like this, Idle has the "-n" switch which means roughly "no
subprocess." If you are on windows (I have no idea what system you are
running on), you can create a shortcut like I have (I call it Py24One).
I just copied the Idle shortcut, and changed the "target"
from:
C:\Python24\pythonw.exe C:\Python24\Lib\idlelib\idle.pyw
to:
C:\Python24\pythonw.exe C:\Python24\Lib\idlelib\idle.pyw -n

That "target", by the way, can also be typed directly to the command
line to start Idle in "no subprocess" mode.

The big advantage to using Idle this way is that (because Idle is
already running a display loop), you can see the effects of your
commands immediately. So the comments in your intro will hold true.

--Scott David Daniels
scott.daniels@acm.org