[Tutor] Why does this function execute before being called?

[Alan Gauld]

On 07/11/15 04:34, Chris Roy-Smith wrote:

> def genF(ofield): ...
>      for x in range(10):

> def second():
>      main=Toplevel(root)
>      ofield=Text(main, height=15, width=15)
>      ofield.pack()
>      B3=Button(main, text='exit', command=main.destroy)
>      B3.pack()
>      B4=Button(main, text='fill text', command=genF(ofield))

You call a function by sup[plying the parens after its name.
So the function gets called here. The normal way to circumvent
that in Tkinter is to use a lambda expression to defer execution,
like so:

B4=Button(main, text='fill text', command=lambda wgt=ofield : genF(wgt))

>      B4.pack()
>      main.mainloop()

I'm not sure you need the second mainloop. I think the
root level mainloop will work for your window too.


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Alan G
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