Page 258 -

building a graphical user interface

Q: So pygame is a library created Q: What’s the deal with the wait_ Q: So the wait_finish() function is

by some programmer other than the finish() function in the Ready Bake like an artificial delay after each sound?
Python folks? Code? I just don’t get why it’s there.
A: No, not really a delay, more like a
A: Yes, it’s what’s called a third-party A: It’s a function that waits for the sound pause designed to let the sound effect play
library. It wasn’t created by you or the to finish playing before continuing with the fully before trying to play anything else.
people that bring you Python. Some other rest of the program. The wait_finish() function forces
programmer(s), a third party, created your sound chip to finish with one sound
pygame. Q: What?! Surely the sound just before starting another. What happens is
Q: And it’s just given away for free? plays? that when a sound is played, the play()
method passes back the channel (or track)
A: Playing with pygame in this way, number that the sound is playing on. You
A: Yes. Which is very nice of them, isn’t although fun, masks a problem that can can then use the channel number to ask
it? surface when working with sound (in any pygame to wait for the channel to finish
playing a sound before continuing, which
Q: Are there other libraries like programming language). It turns out that, is what the code in the Test Drive on the
when asked to play a sound, the main chip
pygame that can be added into my inside your computer (the CPU) doesn’t previous page does.
Python environment? even bother trying. Instead, there’s another, Q:
smaller chip in your computer that is And if I don’t use wait_finish(),
specifically designed to play sounds and what happens then?
A: Yes, there are lots. To see the current it is to this chip that your main chip hands
list, follow the Package Index link from the sound file to and says: “play this for
the main Python website. Python refers to me.” The main chip then goes back to A: All the sounds attempt to play at the
third-party libraries as “packages” and, as running your code, sees another request same time and it sounds like a jumble of
you’ll see, there are packages available for to play a sound, doesn’t bother, hands sounds as opposed to one sound playing,
every conceivable purpose, not just playing the new sound file off to the sound chip, then another, then another, and so on.
sounds or developing games (as is the and repeats until your program ends. The
case with pygame). sound chip—and this is the important
Q: The sounds I downloaded are part—is designed to operate in parallel

WAV files. I know that WAV is one of the with your main chip. While your main chip
is doing something else, the sound chip is
standards for encoding sound, but is it busy playing any sounds it has been asked
the best format to use? to play. And—here’s the rub—if the sound
chip has been asked to play more than one
A: That depends on who you ask! We sound, it attempts to play each sound at
are using WAV files because they are used the same time.
in lots of places and are well-supported on
most operating systems. There are lots of
file formats for sound and many of them
claim to be “better” than WAV, but for what
we are doing here, WAV is perfect.

you are here 4 223