Re: [pygame] Re: Newbie wants to create pong

[Ville Sokk <villes@xxxxxxxxxxxx>]

> Chris Ashurst wrote:
>> Others can help you with your coding issues, but in the meantime, I have
>> a
>> well-commented example of Pong on my server that could possibly provide
>> a
>> reference for you: http://telestatic.net/python/pong.py
>>
>> -----Original Message-----
>> From: owner-pygame-users@xxxxxxxx [mailto:owner-pygame-users@xxxxxxxx]On
>> Behalf Of Ville Sokk
>> Sent: Monday, September 11, 2006 10:21
>> To: pygame-users@xxxxxxxx
>> Subject: [pygame] Re: Newbie wants to create pong
>>
>>
>>
>>> I'm new to programming but I've learned the basics and have done some
>>> programs but now I've decided to learn pygame. I thought I'll make a
>>> simple pong game. I have a wierd bug I can't solve at execution. I
>>> don't
>>> want you to solve other bugs, because I want to learn through solving
>>> myself ;). Sorry for the .zip and Windows newlines. I currently have no
>>> choice but use Windows.
>>>
>>
>> Help? I uploaded it here: http://commodore.gran.ee/asjad/pong.zip too.
>>
>>
>>
> Notes:
>
> #begin code excerpt
> class bg(pygame.sprite.Sprite):
> ......
> [snip]
> .......
> ball=ball()
> batter=batter()
> enemyBatter=enemyBatter()
> allThings=pygame.sprite.RenderPlain((bg, ball, batter, enemyBatter))
> #end excerpt
>
> On the last line you're creating a pygame.sprite.RenderPlain, but look
> what you're passing it.
> what is bg?
> Well, we start at the line where this call is made, and we search back
> up through the code
> until we find the last place 'bg' was defined.
> Oops, it turns out 'bg' is a class, not an instance of a class!
> That's the first problem you're having.
> You can see this error in the traceback:
>
> Traceback (most recent call last):
>   File "C:\Documents and Settings\Rabidpoobear\Desktop\Pong\pong.py",
> line 79, in -toplevel-
>     allThings=pygame.sprite.RenderPlain((bg, ball, batter, enemyBatter))
>   File "C:\Python24\Lib\site-packages\pygame\sprite.py", line 368, in
> __init__
>     self.add(*sprites)
>   File "C:\Python24\Lib\site-packages\pygame\sprite.py", line 241, in add
>     sprite.add_internal(self)
> AttributeError: 'tuple' object has no attribute 'add_internal'
>
> what it's basically saying is 'in the call to pygame.sprite.RenderPlain
> you passed us a 'tuple' object,
> and tuples don't have an 'add_internal' function in them.
> The tuple that you're passing to it is the class 'bg.'  I'm not really
> sure why it considers this a tuple,
> but that's not the point.
> So when you change bg to an instance of a class whose parent is
> pygame.sprite.Sprite, it will
> magically work :)
>
>
> Secondly:  Your ball, batter, and enemyBatter classes have instances
> that are named
> ball, batter and enemyBatter, respectively.
> Effectively, this overwrites the class definitions, so you might as well
> have not made a class in the first
> place and just made one instance  (assuming this is possible in Python,
> I've never tried.).
> Make your class instances different names so you can reuse your code.
> That's the main goal of the OOP paradigm.
>
>
> Another note:
> Your functions, moveBoth, ballReset, etc.
> You're leaving it up to the person to define what a ball, batter and
> other objects are, globally,
> before they call your function.
> A function should be a self-contained thing if possible.  Either your
> function is only side-effects
> or your function is only a return value, I think, is what you're going
> for.  However, I believe
> this mostly applies to functional programming languages and not to
> Object Oriented langauges.
> I don't think you should ever need side-effects or global variables.
> That's what classes are for :D
> I'd suggest making your moveBoth function into a 'reorienty' function
> that accepts any number of parameters and sets all of their y-values
> equal.
> The point being here that it doesn't have to know anything about the
> variables outside
> its local scope, because you're handing it all the information it needs.
>
> Anytime you find yourself typing 'global' there's probably a better way
> to do it.
>
> Especially in your ball class, in the 'fly' function, you check to see
> if the ball and the batter collided.
> However, you didn't get these values passed into the class, you're
> depending on them already being defined
> in the scope from which you call the ball.fly function.
> This is bad news.
>
> It seems like what you need is an overarching 'Game' class that holds
> instances of
> all your other classes, the pygame display surface, etc, etc. all as
> instance-level variables
> so you can safely access them from within each individual function.
> :D
>
> Good luck!
> -Luke
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>

Thanks everyone! Especially you Luke! You wrote such a long post just for
a wannabe-kid-programmer. And you too who gave me that example :P.
Anyways, why don't you people have a forum? I always see UNIX people using
mailing lists. Aren't forums more comfortable?