Update Label Text in Python TkInter

Question

Is there any possible way to create a TkInter label that uses a string and a variable as the text?

For example:

name = \"bob\"
Label(root, text=\"hel         


        

Answer 1

Yes -- standard Tkinter <variable>-s mechanics does that:

There is a Tkinter StringVar() ( and similarly IntVar(), DoubleVar(), BoolVar() ) object constructor, that prepares a smart object that is ready to be later used for this very purpose in Tkinter Widgets.

You may use .set() / .get() methods for manipulating with such object's value(s).

name              = StringVar()        # this creates a Tkinter object
name.set( "bob" )                      # .set() assigns / .get() retrieves
L = Label( root, textvariable = name ) # makes the  used in Label Widget

Label text gets changed right by a new value gets assigned in <variable>

name.set( "alice" )                    # .set() assigns a new value -> promoted
print L['text']                        # show, a value has been promoted in L

FYI: Advanced <variable>-s' Tools

You may also want to know about a more advanced tools for Tkinter variables. There are also more powerfull tools associated with Tkinter variables -- called trace-er(s) -- which set the Tkinter system to "watch" any change to a "traced" variable and this can associate further automated responsive activities, automatically launched upon a traced-event-type.

aWriteTraceID = name.trace_variable( "w", f2CallOnWriteAccessToTracedVariable )
aRead_TraceID = name.trace_variable( "r", f2CallOnRead_AccessToTracedVariable )
aDel__TraceID = name.trace_variable( "u", f2CallOnDel__AccessToTracedVariable )

name.trace_vinfo()                        # show all associated <>

>>> name.trace_vinfo()
[('u', '12945528f2CallOnDel__AccessToTracedVariable'),
 ('r', '12251384f2CallOnRead_AccessToTracedVariable'),
 ('w', '12760924f2CallOnWriteAccessToTracedVariable')
]

name.trace_vdelete( aRead_TraceID )       # delete an identified <>
name.trace_vdelete( aWriteTraceID )       # delete an identified <>

del( name )                               # del() makes name undefined
# so this will "auto-launch" the last, still active <>
# you assigned above -- the function f2CallOnDel__AccessToTracedVariable()

This instrumentation helps you create your GUI toolbox strategies very powerfull for an efficient, event-driven, fully self-reflecting layered [Model-Visual-Controller], supervised under the hood of the Tkinter.mainloop() scheduler

How to put it together?

As abarnert has proposed, the automated version may look in principle like this

name = StringVar()                         # a pure name holder
show = StringVar()                         # a post-processed text

L = Label( root, textvariable = show )     # L will display a post-processed string
L.pack()                                   # L goes into GUI framework's geometry manager

#                                          # prepare the <> function
def autoProcessAndPropagateOnNameVarCHANGE( p1, p2, p3, p4 = name, p5 = show ):
    #                                      # this function will get called
    #                                      # upon WRITE-ACCESS <>
    #
    # .set( a post-processed value ) into [show], that is connected to GUI[Label]
    p5.set( "Hello, " + p4.get() )         
    #                                      # Always be carefull not to fire
    #                                      # an unstoppable chain-reaction ;)
    #                                      # of <>-related events
    #                                      # as more <>-s get used

#                                          # create <> / <> pair
aWriteTraceID = name.trace_variable( "w", autoProcessAndPropagateOnNameVarCHANGE )

# -------------------------------------------------------------------------------
# test <>:
name.set( "Craig" )                        # <>-watched WRITE-ACCESS
# test <> result: GUI Label L shall show "Hello, Craig" -----------------

# -------------------------------------------------------------------------------
# erase all <>-s assigned:
name.trace_vinfo()                         # initial state of <>-s

for aTracerRECORD in name.trace_vinfo():
    name.trace_vdelete( aTracerRECORD[0], aTracerRECORD[1] )

# erase [[[DONE]]] --------------------------------------------------------------
name.trace_vinfo()                         # final   state of <>-s