[Tutor] Tkinter_Entry_tip words

[Alan Gauld]

On 08/12/15 15:08, Yuehua HU wrote:

> I’ve tried to write 'user changing their mind and blanking the field’ case, but it seems not working…
> Did I use '<KeyPress-Delete>’ wrong?

Delete is the key that deletes the character to the right of cursor.
Did you maybe mean to use <'Keypress-BackSpace'>? Or even both of them?

> ...Why should we use a parameter in the function 'greyText(e)’ ? 

Because the bind mechanism passes the event object as an argument
and expects the function to accept it even if its not used.
[Aside: This is annoying since the command attribute of widgets expects
a function with no arguments! To get round that set a default value of None:

def aCallBack(event=None):...

then you can use aCallBack() in either scenario.
]

HTH

> #######################
> import Tkinter
> 
> def checkEnterStrLen(e):
>     if len(var.get())==0:
>         entry.config(fg= 'grey')
>         entry.insert(0, 'help text')
> 
> def greyText(e):
>     entry.config(fg = 'grey')
> 
> def startEntry(e):
>     entry.delete(0,Tkinter.END)
>     entry.config(fg = 'black')
>     entry.unbind('<Key>')
> 
> top = Tkinter.Tk()
> 
> var = Tkinter.StringVar()
> entry = Tkinter.Entry(top, textvariable = var)
> entry.insert(0,'help text')
> 
> entry.bind('<Button-1>', greyText)
> entry.bind('<KeyPress-Delete>',checkEnterStrLen)
> entry.bind('<Key>',startEntry)
> 
> entry.pack()
> 
> top.mainloop()

-- 
Alan G
Author of the Learn to Program web site
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