Getting the choice of optionmenu right after selection Python

Trace the StringVar.

from Tkinter import *def option_changed(*args):    print "the user chose the value {}".format(variable.get())    print amaster = Tk()a = "Foo"variable = StringVar(master)variable.set("Apple") # default valuevariable.trace("w", option_changed)w = OptionMenu(master, variable, "Apple", "Orange", "Grapes")w.pack()mainloop()

Here, option_changed will be called whenever the user chooses an option from the option menu.

You can wrap the trace argument in a lambda to specify your own parameters.

def option_changed(foo, bar, baz):    #do stuff#...variable.trace("w", lambda *args: option_changed(qux, 23, "hello"))

When I come across widgets with annoying interfaces - such as OptionMenu, I generally will write a class around it to abstract away the annoying attributes. In this case, I really dislike the verbosity of using the StringVar every time I want to create a dropdown, so I simply created a DropDown class which includes the StringVar within the class (written in Python 3.5, but translates easily to all):

class DropDown(tk.OptionMenu):    """    Classic drop down entry    Example use:        # create the dropdown and grid        dd = DropDown(root, ['one', 'two', 'three'])        dd.grid()        # define a callback function that retrieves the currently selected option        def callback():            print(dd.get())        # add the callback function to the dropdown        dd.add_callback(callback)    """    def __init__(self, parent, options: list, initial_value: str=None):        """        Constructor for drop down entry        :param parent: the tk parent frame        :param options: a list containing the drop down options        :param initial_value: the initial value of the dropdown        """        self.var = tk.StringVar(parent)        self.var.set(initial_value if initial_value else options[0])        self.option_menu = tk.OptionMenu.__init__(self, parent, self.var, *options)        self.callback = None    def add_callback(self, callback: callable):        """        Add a callback on change        :param callback: callable function        :return:         """        def internal_callback(*args):            callback()        self.var.trace("w", internal_callback)    def get(self):        """        Retrieve the value of the dropdown        :return:         """        return self.var.get()    def set(self, value: str):        """        Set the value of the dropdown        :param value: a string representing the        :return:         """        self.var.set(value)

Example usage:

# create the dropdown and grid, this is the ONLY required codedd = DropDown(root, ['one', 'two', 'three'])dd.grid()# optionally, define a callback function that retrieves the currently selected option then add that callback to the dropdowndef callback():    print(dd.get())dd.add_callback(callback)

Edited to add: Not long after creating this post, I got annoyed with a few other attributes of tk and ended up creating a package called tk_tools to make dropdowns and checkbuttons easier along with addressing other annoyances.