Getting the choice of optionmenu right after selection Python

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暖寄归人
暖寄归人 2021-02-06 17:44

I was wondering if there is any way for me to see what the User has selected among the list displaying, let\'s say: [\"Apple\",\"Orange\",\"Grapes\"] right after th

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  •  误落风尘
    2021-02-06 18:14

    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 code
    dd = DropDown(root, ['one', 'two', 'three'])
    dd.grid()
    
    # optionally, define a callback function that retrieves the currently selected option then add that callback to the dropdown
    def 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.

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