Getting value from Tkinter entry widget: variable scope difficulty

**jim-on-linux** · Nov 20 '06, 04:25 AM

Re: Getting value from Tkinter entry widget: variable scope difficulty

Kevin,
if the present value of searchterm is what you
want, I suggest you make a class

class Kgui:
def __init__(self) : # init self
self.makeGUI()

def makeGUI(self):

###lots of code to set up toplevel windows

searchbutton=Bu tton(topframe,
image=searchgla ss, command=self.do Something)
searchbutton.im age=searchglass
searchbutton.pa ck(side=LEFT, expand = NO)

# and all the resrt of the code

def doSomething(sel f):

file = os.popen('syste mcommand %s' %
searchterm, 'r')

self.searchterm = searchterm

print self.searchterm #used inside the class

Kgui.searchterm = searchterm

print Kgui.searchterm #used outside the class

you can also do;
Kgui.searchterm = self.searchterm = searchterm

I think this is what you are asking for.

jim-on-linux

http://www.inqvista.com

On Sunday 19 November 2006 21:18, Kevin Walzer
wrote:

I'm trying to construct a simple Tkinter GUI
and I'm having trouble with getting the value
of an entry widget and passing it onto a
callback function. But I'm not grokking
variable scope correctly.
>
I have two functions. Here are the relevant
excerpts:
>
def makeGUI():
>
###lots of code to set up toplevel windows
>
searchbutton=Bu tton(topframe,
image=searchgla ss, command=doSomet hing)
searchbutton.im age=searchglass
searchbutton.pa ck(side=LEFT, expand = NO)
>
searchterm=Stri ngVar()
>
entryterm=Entry (topframe,
textvariable=se archterm)
entryterm.pack( side=RIGHT)
>
entrylabel=Labe l(topframe, text="Search:")
entrylabel.pack (side=RIGHT)
>
>
def doSomething():
>
file = os.popen('syste mcommand %s' %
searchterm, 'r')
>
print searchterm
>
---
>
What I want to happen is the value of
searchterm to be passed on to the doSomething()
call when the searchbutton is pressed. Right
now it appears the value of "searchterm " is
local to each function.
>
In Tcl this would be handled by simply
assigning the variable "searchterm " to the
global namespace in each function, i.e. "global
searchterm." I've looked and can't quite figure
out how to do this in Python. Any advice is
appreciated.
>
--
Kevin Walzer
Code by Kevin
http://www.codebykevin.com

**Hendrik van Rooyen** · Nov 20 '06, 06:15 AM

Re: Getting value from Tkinter entry widget: variable scope difficulty

"Kevin Walzer" <kw@kevin-walzer.com>

I'm trying to construct a simple Tkinter GUI and I'm having trouble with
getting the value of an entry widget and passing it onto a callback
function. But I'm not grokking variable scope correctly.
>
I have two functions. Here are the relevant excerpts:
>
def makeGUI():
>
###lots of code to set up toplevel windows
>
searchbutton=Bu tton(topframe, image=searchgla ss, command=doSomet hing)
searchbutton.im age=searchglass
searchbutton.pa ck(side=LEFT, expand = NO)
>
searchterm=Stri ngVar()

this will make a new local variable - if you want to assign to the global one,
you need to add a global statement before doing this, in this makeGUI function.
- you can read the global here if you have defined searchterm in an outer scope,
but the assign will make a new local one.

>
entryterm=Entry (topframe, textvariable=se archterm)
entryterm.pack( side=RIGHT)
>
entrylabel=Labe l(topframe, text="Search:")
entrylabel.pack (side=RIGHT)
>
>
def doSomething():
>
file = os.popen('syste mcommand %s' % searchterm, 'r')

here searchterm seems to be a command line variable.
look in the help for sys.argv how to access command line variables

- not that you need to, but its good to know... :-)

had makeGUI been a class instead of a function, you could have
written makeGUI.searcht erm here, without mucking around with globals....

>
print searchterm
>
---
>
What I want to happen is the value of searchterm to be passed on to the
doSomething() call when the searchbutton is pressed. Right now it
appears the value of "searchterm " is local to each function.
>

True

In Tcl this would be handled by simply assigning the variable
"searchterm " to the global namespace in each function, i.e. "global
searchterm." I've looked and can't quite figure out how to do this in
Python. Any advice is appreciated.

global searchterm # - in outer scope

global searchterm # - in inner scope before assign

HTH - Hendrik

Getting value from Tkinter entry widget: variable scope difficulty

Getting value from Tkinter entry widget: variable scope difficulty

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