[Tutor] Global name not found, though clearly in use

[Corey Richardson]

  I was under the impression that when you define a function, it doesn't 
try to evaluate anything yet. If I had called the function before I 
defined the variable, I would understand, but I haven't. The entirety of 
my (incomplete and buggy) code is now available here: 
http://pastebin.com/QTNmKYC6

Steven D'Aprano wrote:
> On Thu, 15 Jul 2010 12:18:58 am Corey Richardson wrote:
>   
>> Hey tutors. Two separate submissions one day, guess I'm getting busy
>> ;)
>>
>> Anyway, I'm re-writing my hangman program to make use of my new-found
>> understanding of OOP, and using a GUI this time around. I decided on
>> coding with Tkinter, to get my feet wet with GUI stuff.
>>     
>
> With respect, I'm not sure your new-found understanding is that 
> complete, if you're having problems with simple variables. Have you 
> considered doing some basic tutorials to ensure your understanding of 
> Python has a solid foundation?
>
>   
>> Here is the traceback:
>>
>> Traceback (most recent call last):
>>   File "C:\Python31\lib\tkinter\__init__.py", line 1399, in __call__
>>     return self.func(*args)
>>   File "C:/Users/Corey/Desktop/HangmanApp.py", line 45, in getLetter
>>     self.guess = eWordEntryBox.get()
>> NameError: global name 'eWordEntryBox' is not defined
>>
>> However, not even 30 lines down, (29, to be exact) there is this
>> line: eWordEntryBox = tk.Entry(fWordEntry)
>>     
>
> Without seeing your actual code, it's impossible to say what's going on 
> except in vague generalities. But consider a program made of just TWO 
> lines:
>
> print(x)
> x = 1
>
> What do you expect will happen? If you are surprised that Python will 
> raise NameError when it tries to print the value of x, then you really 
> should do some basic tutorials.
>
> At the point that the line "print x" is called, x hasn't been defined 
> *yet*, and so it doesn't exist. My guess is that your error is exactly 
> the same -- you might have a line that defines eWordEntryBox 29 lines 
> further down, but at the point that the error occurs, that line hasn't 
> been reached yet, and so eWordEntryBox doesn't exist:
>
> self.guess = eWordEntryBox.get()  # Error occurs here
> ...
> ...
> 29 lines of code
> ...
> ...
> eWordEntryBox = tk.Entry(fWordEntry)  # Defined for the first time!
>
>
>   
>> Not understanding what is happening here. Same happens when I tack
>> self at the beginning of it, except it says global name self is not
>> defined.
>>     
>
> You can't just "tack" self at the beginning of variables and expect it 
> to work, any more than you could tack on "akjfhbcvgsaj" and hope for 
> the best! You need to understand *where* the variable self exists, and 
> *what* value it has.
>
>
>
>
>   
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