[Tutor] Passing a Variable

[bob gailer]

On 4/3/2011 9:55 PM, Ryan Strunk wrote:
> Hi list,

Hi

I've read your code. Frankly I don't understand your problem. I also 
don't see any occurrence of "health".

Could you point to a specific line of code, explain what you want and 
what you are getting.

Also your description of the program and the program itself is kinda 
overwhelming, and so much of that information is not relevant to your 
question. That makes it hard to understand the question.

How about posting the smallest possible piece of code that exemplifies 
the problem?

Python does not "pass by value". It passes a reference to the argument. 
In essence:

def foo(a): pass
b = somePythonObject # b is now a reference to somePythonObject
foo(b)

In calling the function Python "binds" local name a to somePythonObject
a is now another reference to somePythonObject

> I am in the midst of trying to code a game based entirely on audio cues, and
> I've run into a bit of a snag when trying to monitor certain variables. I'll
> lay out the framework of what I'm going for in the hope that it makes sense
> when written down.
> In a standard video game I could have a health bar go from normal to yellow
> to red as it diminishes. In audio, though, I don't have that luxury. As a
> result, I have conceptualized a system whereby a player hears a sound every
> so often if a particular stat drops into the caution range. If the player
> drops into the danger range, the sound loops continuously. I also wanted to
> make sure that if the player dropped from caution to danger, there wasn't a
> big, awkward pause in the sound loop and that the player would know
> immediately that his stat had dropped (see first and second if checks in the
> check method).
> The problem:
> My existing methods directly update stats. For example: the player class has
> a self.health stat which is directly affected by other methods. This has
> caused no problem up until now. When I pass self.health to the code I will
> paste below, however, the Statistic class does not receive health, but
> rather health's value.
> I understand that python passes variables by value and not by reference, and
> this has not been a problem up until now. Now that I am trying to design a
> class which explicitly checks a specific variable, though, I can't fathom a
> way to do it unless I pass a direct reference, and I'm not sure that can be
> done. I need to figure out a way for the below code to check the value of
> the health variable and act on it. This way, if player's self.health
> changes, the static class will take note of that and respond accordingly.
> It occurred to me to make Statistic a child of int, but I'm told that's more
> trouble than I probably want to deal with.
> Any suggestions/advice anyone has would be greatly appreciated.
>
> Best,
> Ryan
>
> import sound_lib
> from game_utils import delay
> #this encapsulates threading.Timer's assignment and start method
>
> class Statistic(object):
>
>      def __init__(self, stat=None, sound=None, low=None, mid=None,
> high=None):
>          self.stat = stat
>          self.sound = sound
>          self.low = low
>          self.mid = mid
>          self.high = high
>          self.status = 'safe'
>          self.auto_check_timer = None
>
>      def auto_check(self):
>          if self.stat>  self.high:
>              self.status = 'safe'
>              return
>          if self.mid<= self.stat<= self.high:
>              self.status = 'caution'
>              self.sound.play(True)
>              self.auto_check_timer =
> delay(self.sound.bytes_to_seconds(len(self.sound))*2, self.auto_check)
>              return
>          if self.low<= self.stat<  self.mid:
>              self.status = 'danger'
>              self.sound.play(True)
>              self.auto_check_timer =
> delay(self.sound.bytes_to_seconds(len(self.sound)), self.auto_check)

You can simplify the above logic:

          if self.stat > self.high:
              self.status = 'safe'
          elif self.stat >= self.mid:
              self.status = 'caution'
              self.sound.play(True)
              self.auto_check_timer = 
delay(self.sound.bytes_to_seconds(len(self.sound))*2, self.auto_check)
          elif self.stat >= self.low:
              self.status = 'danger'
              self.sound.play(True)
              self.auto_check_timer = 
delay(self.sound.bytes_to_seconds(len(self.sound)), self.auto_check)
>      def check(self):
>          if self.status = 'caution' and self.low<= self.stat<  self.mid:
>              #This will set the program to start a constant alarm when the
> stat level has dropped below caution
>              self.auto_check_timer.cancel()
>          if self.sound.is_playing:
>              #to assist in setting up the caution to danger transition
>              #a standard playing sound will have a timer running alongside
> it, so skip the next guard and return
>              if self.auto_check_timer.is_alive() == False:
>                  #guard to make sure program doesn't catch every playing
> sound, should prevent repeated checks from recalling auto_check
>                  sound_duration =
> self.sound.bytes_to_seconds(len(self.sound)) -
> self.sound.bytes_to_seconds(self.sound.position)
>                  self.auto_check_timer = delay(sound_duration,
> self.auto_check)
>              return
>          if self.auto_check_timer == False:
>              #if the timer has never been called, call auto_check
>              self.auto_check()
>              return
>          if self.auto_check_timer.is_alive == True:
>              #there's already a timer running. return
>              return
>          #If it gets this far, it's because the timer already ran, the player
> is 'safe', and another check is being performed
>          self.auto_check()
>
Also note

if self.auto_check_timer == False:

can be simplified to

if not self.auto_check_timer:


and

if self.auto_check_timer.is_alive == True:

to

if self.auto_check_timer.is_alive:

also it is better to eliminte the returns and use elif as I did furhter 
above

-- 
Bob Gailer
919-636-4239
Chapel Hill NC