tkinter global variable

Fri Nov 13 23:25:31 EST 2020

On 2020年11月13日 18:40:53 +0100, David Kolovratník wrote:
> On Fri, Nov 13, 2020 at 05:12:10PM +0000, ChalaoAdda wrote:
>> On 2020年11月13日 12:04:53 -0500, Richard Damon wrote:
>>>> > On 11/13/20 11:42 AM, ChalaoAdda wrote:
>> >> On 2020年11月13日 16:04:03 +0000, Stefan Ram wrote:
>> >>
>> >>> ChalaoAdda <chalao.adda at gmail.com> writes:
>> >>>> On 2020年11月13日 15:41:20 +0000, Stefan Ram wrote:
>> >>>>> ChalaoAdda <chalao.adda at gmail.com> writes:
>> >>>>>> I am trying to read a file from askopenfilename outside the
>> >>>>>> function.
>> >>>>>> I am getting blank file name. What am I doing wrong? Here is my
>> >>>>>> code.
>> >>>>> It is possible that you try to read from "pic" before
>> >>>>> "on_openfile"
>> >>>>> ever was executed.
>> >>>> I didn't get you. I click on the menu item "Open" and then from
>> >>>> the filedialog select a file. And then outside that function I am
>> >>>> trying to read and print the file.
>> >>> I have added two additional statements to your source code:
>> >>> print( "A" ) and print( "B" ).
>> >>>
>> >>> If you now execute this new source code, you might observe that
>> >>> "B"
>> >>> is being printed before "A" is being printed.
>> >>>
>> >>> from tkinter import *
>> >>> from tkinter import filedialog
>> >>>
>> >>> def on_openfile():
>> >>> print( "A" )
>> >>> global pic pic = filedialog.askopenfilename()
>> >>>
>> >>>
>> >>> root = Tk()
>> >>>
>> >>> menubar = Menu(root)
>> >>> root.config(menu=menubar)
>> >>> file_menu = Menu(menubar) file_menu.add_command(label="Open",
>> >>> command=on_openfile) file_menu.add_command(label="Exit",
>> >>> command=root.destroy)
>> >>> menubar.add_cascade(label="File", menu=file_menu)
>> >>>
>> >>>
>> >>> print( "B" )
>> >>> f = open(pic)
>> >>> print(f.read())
>> >>>
>> >>> root.mainloop()
>> >> Ok. I got the point. So what do I need to do access the variable?
>> >> How do I return a value from that function?
>> >>
>> >> Thanks.
>> > 
>> > The problem is that you are accessing the variable BEFORE the box has
>> > been put up and the user clicking on it. That doesn't happen until
>> > the mainloop() call. You need to delay the opening and reading of the
>> > file till the filedialog has been used and returned.
>> > 
>> > Perhaps on_openfile could open and read the file.
>>>> Ok. Then how do I access the content of the file from outside the
>> function? How can I access return value?
>> Thanks.
> What about
>> def on_printfilename():
> global pic try:
> print( f"C: {pic}" )
> except NameError:
> print( f"C! pic not set yet" )
>> together with
>> file_menu.add_command(label="Print filename", command=on_printfilename)
>> Or move your print("B") block behind the mainloop().
>> David

Thanks. That solved my problem.
Thanks.