[Tutor] Python and Tkinter (total newbie)

[Dave Angel]

On 12/09/2011 02:03 PM, Richard Lyons wrote:
> I have tried to enter the first sample program from p. 19 in Grayson:
> Python and Tkinter Programming.  When I run the program I get an error
> as follows:
>
> Traceback (most recent call last):
>  File "/home/dick/Desktop/calc1.py", line 50, in <module>
>    if _name_ == '_main_':
> NameError: name '_name_' is not defined
>
> The error makes sense because nowhere in the code is _main_ defined.
> How do I fix this?
>
>
> from Tkinter import *
> def frame(root, side):
>    w = Frame(root)
>    w.pack(side=side, expand=Yes, fill=BOTH)
>    return w
>
> def button(root, side, text, command=NONE):
>    w = Button(root, text+text, command+command)
>    w.pack(side=side, expand=YES, fill=BOTH)
>    return w
>
> class Calculator(Frame) :
>    def _init_(self) :
>        Frame._init_(self)
>        self.pack(expand=YES, fill=BOTH)
>        self.master.title('Simple Calculator')
>        self.master.iconname("calc1")
>
>        diplay = StringVar()
>        Entry(self, relief=SUNKEN,
>              textvariable=display).pack(
> side=TOP, expand=YES,
>                                         fill=BOTH)
>
>        for key in ("123", "456", "789", "-0."):
>            keyF = frame(self, TOP)
>            for char in key:
>                button(keyF, LEFT, char,
>                       lambda w=display,s='%s'%char: w.set(w.get()+s))
>
>
>        opsF = frame(self, TOP)
>        for char in "+-*/=":
>            if char == '=':
>                btn = button(opsF, LEFT, char)
>                btn.bind('<ButtonRelease-1>',
>                         lambda e, s=self, w=display: s.calc(w), '+')
>            else:
>                btn = button(opsF, LEFT, char,
>                        lambda w=display, c=char: w.set(w.get()+' '+c+' 
> '))
>
>            clearF = frame(self, BOTTOM)
>            button(clearF, LEFT, 'Clr', lambda w=display: w.set(' '))
>
>    def calc(self, display):
>        try:
>            display,set('eval(display.get())')
>        except ValueError:
>            display.set("ERROR")
>
> if _name_ == '_main_':
>    Calculator().mainloop()
>
The problem is simple:

__name__  has two underscores before,and two underscrores after the 
letters.   You typed only one.

That name is predefined for you in every script and module.  In a script 
it has the value "__main__"  (again with two underscores each place), 
and in a module, it has the module name.

-- 

DaveA