Check OptionMenu selection and update GUI

Question

I'm working on a class project and I'm trying to take it beyond the requirements a little here (I'm doing my own homework, just need help improving it!) so I want to update the GUI based on certain selections the user makes instead of just having all irrelevent options available all the time (requirements are to just present the options).

I'm still new to Python and even more new to Tkinter so my only attempt has been the following:

#Step Type
ttk.Label(mainframe, text = "Step Type").grid(column = 1, row = 16)
type_entry = OptionMenu(mainframe, StepType, "Kill", "Explore" , "Conversation")
type_entry.grid(column = 2, row = 16, sticky = (E))

#Step Goal
if StepType.get() == "Kill":
   ttk.Label(mainframe, text = "Required Kills").grid(column = 1, row = 17)
   goal_entry = ttk.Entry(mainframe, width = 20, textvariable = StepGoal)
   goal_entry.grid(column = 2, row = 17, sticky = (E))
elif StepType.get() == "Explore":
   ttk.Label(mainframe, text = "Location ID").grid(column = 1, row = 17)
   goal_entry = ttk.Entry(mainframe, width = 20, textvariable = StepGoal)
   goal_entry.grid(column = 2, row = 17, sticky = (E))
elif StepType.get() == "Conversation":
   ttk.Label(mainframe, text = "NPC ID").grid(column = 1, row = 17)
   goal_entry = ttk.Entry(mainframe, width = 20, textvariable = StepGoal)
   goal_entry.grid(column = 2, row = 17, sticky = (E))

Obviously what I want to do here is when the user selects one of the options from the menu, to display the corresponding entry box and label instead of having all 3 all the time.

Also looking for the same situation for CheckButton

Answer 1

Full working example: tested od 2.7.5 and 3.3.2

It use command= in OptionMenu to call function when user changed option.

import tkinter as ttk

#----------------------------------------------------------------------

def on_option_change(event):
    selected = step_type.get()

    if selected == "Kill":
        goal_label['text'] = "Required Kills"
    elif selected == "Explore":
       goal_label['text'] = "Location ID"
    elif selected == "Conversation":
       goal_label['text'] = "NPC ID"

    # show label and entry
    #goal_label.grid(column=1, row=17)
    #goal_entry.grid(column=2, row=17, sticky='E')

#----------------------------------------------------------------------

mainframe = ttk.Tk()

# Step Type

step_type = ttk.StringVar() # there is the rule: variable name lowercase with _
ttk.Label(mainframe, text="Step Type").grid(column=1, row=16)
type_entry = ttk.OptionMenu(mainframe, step_type, "Kill", "Explore" , "Conversation", command=on_option_change)
type_entry.grid(column=2, row=16, sticky='E')
step_type.set("Kill")

# Step Goal

step_goal = ttk.StringVar()
goal_label = ttk.Label(mainframe, text="Required Kills")
goal_label.grid(column=1, row=17)
goal_entry = ttk.Entry(mainframe, width=20, textvariable=step_goal)
goal_entry.grid(column=2, row=17, sticky='E')

# hide label and entry
#goal_label.grid_forget()
#goal_entry.grid_forget()

# --- star the engine ---

mainframe.mainloop()

BTW: you can use grid() and grid_forget() to show and hide elements.

---

EDIT: example with Radiobutton using trace on StringVar

import tkinter as ttk

#----------------------------------------------------------------------

def on_variable_change(a,b,c): # `trace` send 3 argument to `on_variable_change`

    #print(a, b, c)

    selected = step_type.get()

    if selected == "Kill":
        goal_label['text'] = "Required Kills"
    elif selected == "Explore":
       goal_label['text'] = "Location ID"
    elif selected == "Conversation":
       goal_label['text'] = "NPC ID"

#----------------------------------------------------------------------

mainframe = ttk.Tk()

# Step Type

step_type = ttk.StringVar() # there is the rule: variable name lowercase with _

ttk.Label(mainframe, text="Step Type").grid(column=1, row=16)

ttk.Radiobutton(mainframe, text="Kill", value="Kill", variable=step_type).grid(column=2, row=16, sticky='E')
ttk.Radiobutton(mainframe, text="Explore", value="Explore", variable=step_type).grid(column=3, row=16, sticky='E')
ttk.Radiobutton(mainframe, text="Conversation", value="Conversation", variable=step_type).grid(column=4, row=16, sticky='E')

step_type.set("Kill")
# use `trace` after `set` because `on_variable_change` use `goal_label` which is not created yet.
step_type.trace("w", on_variable_change)

# Step Goal

step_goal = ttk.StringVar()
goal_label = ttk.Label(mainframe, text="Required Kills")
goal_label.grid(column=1, row=17)
goal_entry = ttk.Entry(mainframe, width=20, textvariable=step_goal)
goal_entry.grid(column=2, row=17, sticky='E')

# --- star the engine ---

mainframe.mainloop()