Adding default value as None for tk.OptionMenu and ttk.OptionMenu positional arguments in order to follow standards and get default non-parameterized widget

[kurawlefaraaz]

Feature or enhancement

Proposal:

In current implementation of .__init__ of tk.OptionMenu, tkinter raise's error if we use

tk.OptionMenu() # Argument missing error

while other widgets like tk.Button work without arguments

 tk.Button() # No Error

Therefore by making the below change, tkinter can follow its standard among other widget as well as let user get a non-parameterized OptionMenu widget.

Change:

def __init__(self, master, variable, value, *values, **kwargs): #Line 4020 in cpython/Lib/tkinter /__init__.py

To:

def __init__(self, master=None, variable=None, value=None, *values, **kwargs): #Line 4020 in cpython/Lib/tkinter /__init__.py

Has this already been discussed elsewhere?

This is a minor feature, which does not need previous discussion elsewhere

Links to previous discussion of this feature:

No response

Linked PRs

• gh-130356: Add default values to the parameters of the widget tkinter.OptionMenu #130479

[Xiaokang2022]

@kurawlefaraaz I agree with you!

I took a look and saw that it looks like only the widget OptionMenu doesn't have default parameters, which is really inconvenient for some situations (e.g. when I just want to quickly create widgets to see the layout, and don't want to specify the exact parameters)

So I created a PR to implement this feature and linked it to this issue.

But using None as the default for some parameters causes some problems, and I changed it to an empty string in the PR.

[kurawlefaraaz]

@Xiaokang2022
I think assigning None as default value for variable option would be more expressive, since variable is to link a tkinter widget and it would make more sense if default value for it to be None rather than a empty string.

I have tested using empty string but that too raises similar exception.

[Xiaokang2022]

@kurawlefaraaz
I agree. It does make more sense to set the default value of the variable parameter to None, but it is better to use a string for the parameter value.

[serhiy-storchaka]

What is the use of an empty OptionMenu? Why do you need it?

OptionMenu is currently implemented in Python (to support the command argument), but it was build to imitate the tk_optionMenu Tk command:

tk_optionMenu pathName varName value ?value value ...?

The variable name is mandatory, and at least one value should be specified. Empty value is not the same as absent value.

ttk.OptionMenu allows to not specify any value, but the variable argument is still mandatory, and there is set_menu() method which allows to change the set of options dynamically.

[kurawlefaraaz]

@serhiy-storchaka I agree that empty value is not same as no value, therefore in that case the value option would be defaulted as None.

if someone just wants to see the a default OptionMenu and does not want it to be functional then empty OptionMenu would be useful. In current implementation of OptionMenu, the programmer is required to create a tkinter variable object and then assign it(or exiplcitly assign None), but that's not useful if someone does not want to OptionMenu to be functional and just wants to see how a default OptionMenu looks.

tk.Button() is perfect example for it since if no arguments are passed, it just adds the button to Tk() and all other values are defaulted by the Tk and not tkinter.

I also noticed that a workaround exist to get default OptionMenu for both tkinter and tkinter.ttk:

tk.OptionMenu(None, None, None) # Raises error "set" command not avialable for NoneType object when we select an item in dropdown menu
ttk.OptionMenu(None, None, None) # No error since this does not show a dropdown menu

This also lets tkinter standardize all of its widget.

[serhiy-storchaka]

Closing due to absent of use cases.

[kurawlefaraaz]

@serhiy-storchaka
Since I am new to GitHub and open source community, can you describe how to determine if some issue is having a worthy use case? This would help me learn and improve my interaction with the opensource community in the future.

[serhiy-storchaka]

As I see, your issue is a learning issue. You should just learn that some constructors has required parameters. It is not possible, for example, to open a file without specifying its name. tk.OptionMenu is not exceptional. You will find that constructors without required parameters are are rather exceptional.

[kurawlefaraaz]

@serhiy-storchaka I hope you are not busy

I think you have misunderstood that I am new to python it self. I have a pretty good experience with python and tkinter and while working on a project of mine(which use's tkinter) I came to know that we can not get a default OptionMenu, to get a default OptionMenu I had to explicitly give arguments to OptionMenu as tk.OptionMenu(None, None, None) which I found a bit awkward. That's the reason I decided to open a Issue.