[Tutor] Class Tips

[Alan Gauld]

"David" <david at abbottdavid.com> wrote

> OK, this is what I came up with, how else could I do it so as not to use 
> sys.exit() ?

You don;t need the exit(), The program  will just drop off the end
silently without it. Thre are several other redundant bits you could
just miss out:

> class FertRate:
>     def __init__(self, rate, nitrogen, acre, bag):
>         self.area = 43.560
>         self.app = rate / (nitrogen / 100.00)
>         self.acre = acre
>         self.bag = bag
>
>     def result(self):
>         result = self.app * self.area * self.acre / self.bag
>         return result

       leave out the variable and just return the calculated value:
            return self.app * self.area * self.acre / self.bag

> def main():
>     while True:
>         try:
>             frate = FertRate( *get_inputs() )
>             result = frate.result()
>             print 'You should apply %0.2f bags.' % result

And here miss the variable and use the functin in the format string:
              print 'You should apply %0.2f bags.' % frate.result()

>             exit()

And just delete this.

>         except TypeError, UnboundLocalError:
>             pass
>
> def get_inputs():
>     try:
>         print 'Rate: Pounds nitrogen per 1000 (square feet)'
>         rate = float(raw_input('Enter Rate i.e., (0.5): '))
>         print "Nitrogen: The first number of the fertilizer's analysis"
>         nitrogen = float(raw_input('Enter Nitrogen From Bag i.e., (14): 
> '))
>         acre = int(raw_input("Enter Total Acre's To Be Treated i.e, (3): 
> "))
>         bag = int(raw_input('Enter Bag Weight (lb): i.e., (50) '))
>         return rate, nitrogen, acre, bag
>     except ValueError:
>         print 'Invalid input!'
>         print 'You must enter a number!'

You could put the whole thing in a while loop so the error gets
printed but the user has a chance to corect it.

def get_inputs():
    while True:
          try:
              # blah blah
              return .....      # breaks from the while loop
          except ValueError, TypeError:
              print blah

HTH,


-- 
Alan Gauld
Author of the Learn to Program web site
http://www.alan-g.me.uk/