[SOLVED] Tkinter menu: trying to use item label in callback

KlaasJan · 08-12-2020, 06:06 AM

Hello,
In a tkinter app I have a two-level menu with book categories, like Exact - Astronomy
or Music - Classic. The second level is added to the first one with add_cascade.
I want to use the labels of any duo in the appropriate command-callback, without writing them litterally in the callback. So far in my experiments I allways get back the labels of the last duo fed into the gui. I do understand now why. But how to get the labels I clicked on ?
KlaasJan

smallpond · 08-12-2020, 09:13 AM

Could you show the code you are trying? One way to pass an argument to a common callback is by using a lambda:

Code:

def myCallback(label):
    print "You clicked on",label 

menubar.add_command(label="Hello", command=lambda: myCallback("Hello"))

KlaasJan · 08-12-2020, 11:07 AM

Thanks for looking at my problem.
I had to translate my script from dutch into my english.
My difficulty is with the dictionary self.rubmap{},
in which each self.rubmap[mainLabel] refers to a menu for this main-label,
and to which are added the sub-labels, each with a command-option.
The script:

#!/usr/bin/env python3

from tkinter import *
from tkinter.ttk import *

class UniMenu():
def __init__(self,root):
self.root = root
geometrie = "800x50+600+200"
self.root.geometry(geometrie)
self.rubric = Label(self.root,text='Rubric:')
self.rubric.pack(side=LEFT)

# make a menu-bar for one item only:
self.uMenu = Menu(self.root,type='menubar')

# fill het hele menu:
self.fillRubric()

# put the newly created rubMenu below uMenu:
self.uMenu.add_cascade(label='click',menu=self.rubMenu)

# display the completed uMenu
self.uMenu.pack(side=LEFT)

def fillRubric(self):
'''
Main-rubrics and sub-rubrics come from a file called 'afdeling',
which means rubric (!).
A part of it looks like this, an indented line is a sub-rubric:

Exact
Wiskunde_statistiek
Informatica
Natuurkunde
Astronomie
Geologie
Biologie
Mens
'''
def show(a,b):
print("Choice: %s: %s" % (a,b))

# maak een vooralsnog onzichtbaar sub-menu rubMenu:
rubricfile = "/kappa/data/afdeling"
self.rubMenu = Menu(self.uMenu,tearoff=0)
self.rubmap = {}
rf = open(rubricfile,'r')
mainRubCounter = 0
subRubCounter = 0
for fileLine in rf:
# a sub-rubric starts in the import-file with at least one space:
mainRubric = False if fileLine.startswith(" ") else True
self.shortLine = fileLine.strip()

if self.shortLine.startswith('#'): continue
if len(self.shortLine) < 1: continue

if mainRubric:

if mainRubCounter > 0:
# A main-rubric can only be cascaded when allof its subs are read,
# at least that is what I think how it works,
# so I made it a one-fase-off procedure.
self.rubMenu.add_cascade(label=self.mainLabel,menu=self.rubmap[self.mainLabel])
print("Menu: rubMenu Index: %s Label: %s" % (self.rubMenu.index(self.mainLabel), self.mainLabel))
self.mainLabel = self.shortLine
mainRubCounter += 1
self.rubmap[self.mainLabel] = Menu(self.rubMenu, tearoff=0)
else:
# command trial: lambda: show(self.mainLabel,self.shortLine))
z = lambda: show(self.mainLabel,self.shortLine)
self.rubmap[self.mainLabel].add_command(label=self.shortLine,command=z)
print("Menu: rubmap[%s] Index: %s Label: %s" % (self.mainLabel,
self.rubmap[self.mainLabel].index(self.shortLine), self.shortLine))
# De last mainRubric, because because mainRubric telkens een achterloopt:
self.rubMenu.add_cascade(label=self.mainLabel,menu=self.rubmap[self.mainLabel])
print("Menu: rubMenu Index: %s Label: %s" % (self.rubMenu.index(self.mainLabel), self.mainLabel))

def doNothing(self):
pass

root = Tk()
root.title('Experiment with a rubric tree')
um = UniMenu(root)
root.mainloop()

,

KlaasJan · 08-12-2020, 11:22 AM

Here is the script again, now hopefully with the original indentation:

Code:

#!/usr/bin/env python3

from   tkinter     import *
from   tkinter.ttk import *

class UniMenu():
    def __init__(self,root):
        self.root = root
        geometrie = "800x50+600+200"
        self.root.geometry(geometrie)
        self.rubric = Label(self.root,text='Rubric:')
        self.rubric.pack(side=LEFT)

        # make a menu-bar for one item only:
        self.uMenu = Menu(self.root,type='menubar')

        # fill het hele menu:
        self.fillRubric()

        # put the newly created rubMenu below uMenu:
        self.uMenu.add_cascade(label='click',menu=self.rubMenu)

        # display the completed uMenu
        self.uMenu.pack(side=LEFT)

    def fillRubric(self):
        '''
        Main-rubrics and sub-rubrics come from a file called 'afdeling',
        which means rubric (!).
        A part of it looks like this, an indented line is a sub-rubric:

        Exact
            Wiskunde_statistiek
            Informatica
            Natuurkunde
            Astronomie
            Geologie
        Biologie
            Mens
        '''
        def show(a,b):
            print("Choice: %s: %s" % (a,b))

        # maak een vooralsnog onzichtbaar sub-menu rubMenu:
        rubricfile = "/kappa/data/afdeling"
        self.rubMenu = Menu(self.uMenu,tearoff=0)
        self.rubmap = {}
        rf = open(rubricfile,'r')
        mainRubCounter = 0
        subRubCounter = 0
        for fileLine in rf:
            # a sub-rubric starts in the import-file with at least one space:
            mainRubric = False if fileLine.startswith(" ") else True
            self.shortLine = fileLine.strip()

            if self.shortLine.startswith('#'): continue
            if len(self.shortLine) < 1: continue

            if mainRubric:

                if mainRubCounter > 0:
                    # A main-rubric can only be cascaded when allof its subs are read,
                    # at least that is what I think how it works,
                    # so I made it a one-fase-off procedure.
                    self.rubMenu.add_cascade(label=self.mainLabel,menu=self.rubmap[self.mainLabel])
                    print("Menu: rubMenu  Index: %s  Label: %s" % (self.rubMenu.index(self.mainLabel), self.mainLabel))
                self.mainLabel = self.shortLine
                mainRubCounter += 1
                self.rubmap[self.mainLabel] = Menu(self.rubMenu, tearoff=0)
            else:
                # command trial: lambda: show(self.mainLabel,self.shortLine))
                z = lambda: show(self.mainLabel,self.shortLine)
                self.rubmap[self.mainLabel].add_command(label=self.shortLine,command=z)
                print("Menu: rubmap[%s]  Index: %s  Label: %s" % (self.mainLabel,
                    self.rubmap[self.mainLabel].index(self.shortLine), self.shortLine))
        # De last mainRubric, because because mainRubric telkens een achterloopt:
        self.rubMenu.add_cascade(label=self.mainLabel,menu=self.rubmap[self.mainLabel])
        print("Menu: rubMenu  Index: %s  Label: %s" % (self.rubMenu.index(self.mainLabel), self.mainLabel))

    def doNothing(self):
        pass


root = Tk()
root.title('Experiment with a rubric tree')
um = UniMenu(root)
root.mainloop()

smallpond · 08-13-2020, 08:51 AM

Thank you for the indented version. My example was too simple. You need to bind the value when the lambda is created so it is not evaluated later.

Code:

z = lambda a=self.shortLine: show(self.mainLabel,a)

KlaasJan · 08-13-2020, 09:34 AM

smallpond, thank you for this eye-opener. I didn't know I could use the lambda arguments in this way.