I mentioned that I figured out how to use a variable with a Python TK Listbox
in my post (http://www.mail-archive.com/python-list@python.org/msg271288.html).
Now, I'm trying to make a class, ListVar, that allows me to operate on a
Listbox's listvariable as if it were a list. The problem is, it doesn't work
as expected some of the time. If I try to add a sequence of simple strings, it
doesn't display anything. If I convert them to a tuple or instantiate a class
(with __str__ defined), then it displays everything - the simple string,
instances, tuples, everything.
I don't understand why it won't show the simple strings, by themselves, in the
Listbox. Notice - the spaces are important. I can make this work without as
much of a headache my strings don't have spaces (which is what the 2 or 3
examples I've been able to find did), but spaces apparently makes this more
complicated.
Can anyone explain what's happening? I'm completely frustrated with trying to
figure this out.
Thanks,
-JB
Here is the simplest working code snippet I felt I could make:
[code]
import Tkinter, tkSimpleDialog
class ListVar( Tkinter.Variable, list ): # Dual inheritance
def __init__( self, master = None, *args, **kw ):
Tkinter.Variable.__init__( self, master )
list.__init__( self, *args, **kw )
self.set( self ) # populate the Tk variable
def get( self ):
value = Tkinter.Variable.get( self )
if( isinstance( value, list ) ):
return value
return list( value )
def set( self, value ):
if( isinstance( value, list ) ):
value = tuple( value )
Tkinter.Variable.set( self, value )
def append( self, item ): list.append( self, item ), self.set( self )
# Class to wrap around a string and make a simple instance.
class sillyString( object ):
def __init__( self, s ): self.myString = s
def __str__( self ): return self.myString
# Dialog class to display a Listbox and test the ListVar class.
class ListboxDialog( tkSimpleDialog.Dialog ):
def __init__( self, master, listItems = [] ):
self.myVar = ListVar( master, listItems ) # Initial set of the list
tkSimpleDialog.Dialog.__init__( self, master, "Listbox testing" )
def body( self, master ):
Tkinter.Listbox( master, listvariable = self.myVar, width = 50 ).grid()
self.myVar.append( "appended string" ) # test append
def __str__( self ): return "%s" % self.myVar.get()
if( "__main__" == __name__ ):
tk = Tkinter.Tk()
tk.withdraw()
# The spaces are important as my listbox will contain strings with spaces.
# The print displays what's in the ListVar after the dialog exits
print ListboxDialog( tk, '' ) # Simple String
print ListboxDialog( tk, [ '' ] ) # list with empty string
print ListboxDialog( tk, [ 'abc string' ] ) # list with short string
print ListboxDialog( tk, [ sillyString( "instance 1" ) ] ) # class instance
print ListboxDialog( tk, [ sillyString( "instance 1" ),
sillyString( "instance 2" ) ] ) # 2 instances
print ListboxDialog( tk, [ ( "A tuple", ),
"A string" ] ) # tuple and string
[/code]
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