[Tutor] My best GUI app so far.

[jfouhy at paradise.net.nz]

Quoting "Jacob S." <keridee at jayco.net>:

> Is there some way that I could loop over those button definitions?

You could try something like this:

        defArgs = { 'width':4,
                    'height':3 }
        # Format: ( label, callback, grid_row, grid_column )
        buttons = [ ('0', self.adddigit0, 5, 1),
                    ('1', self.adddigit1, 4, 1),
                         ...
                    ('x', self.multiply, 3, 4),
                         ...
                    ('M+', self.memplus, 1, 1) ]

        for label, callback, row, col in buttons:
            Button(self, 
                   text=label, 
                   command=callback, 
                   **defArgs).grid(row=row, column=col)

Things to note with this approach:
 - Functions are first-class objects in python, so you can put them in lists and
things.
 - You can convert between dictionaries and keyword arguments (with some
restrictions) by using **.  I like to use this as a way setting default
arguments for buttons and things.  Now, if you want to make your buttons bigger,
you only have to change the code in one place.
 - I'm not "remembering" the buttons as I create them: they are created,
immediately gridded, and then forgotton.  Tkinter still remembers them, so
everything still works.  But I can't (easily) get access to them, if I wanted to
change the labels or anything.  You will have to think about whether this is an
issue when you are coding --- but I don't think it is a problem here.

Also, rather than defining functions adddigit0, adddigit1, etc, you could
instead do:

        def addDigit(self, digit):
            self.ctb()
            self.distext.set(self.distext.get() + str(digit))

and then change your callbacks:

        buttons = [ ('0', lambda : self.addDigit(0), 5, 1),
                    ('1', lambda : self.addDigit(1), 4, 1),
                            ...
                  ]

I remember one of my lecturers saying that if you ever find yourself cutting and
pasting when you are coding, there is something you could do better.

Hope this helps :-)

-- 
John.