On Oct 10, 5:03 pm, Larry Bates <[EMAIL PROTECTED]> wrote:
> Shawn Minisall wrote:
> > I just learned about if, then elif statements and wrote this program.
> > The problem is, it's displaying all of the possibilities even after you
> > enter a 0, or if the fat grams are more then the total number of
> > calories , that is supposed to stop the program instead of continuing on
> > with the print statements that don't apply. Any idea's? thanks
>
> > #Prompt for calories
> > cal = input("Please enter the number of calories in your food: ")
>
> > #Prompt for fat
> > fat = input("Please enter the number of fat grams in your food: ")
>
> > #Input validation
> > if cal or fat <= 0:
> > #Display message
> > print "Error. The number of calories and/or fat grams must be
> > positive"
> > print
>
> > else:
> > #Calculate calories from fat
> > calfat = float(fat) * 9
> > #Calculate number of calories from fat
> > caldel = calfat / cal
>
> > #change calcent decimal to percentage
> > calcent = caldel * 100
>
> > if calfat > cal:
> > print "The calories or fat grams were incorrectly entered."
>
> > else:
> > #evaluate input
> > if caldel <= .3:
> > print "Your food is low in fat."
> > elif caldel >= .3:
> > print "Your food is high in fat."
>
> > #Display percentage of calories from fat
> > print "The percentage of calories from fat in your food is %",
> > calcent
>
> > Here's an example of the output...
>
> > Please enter the number of calories in your food: 50
> > Please enter the number of fat grams in your food: 30
> > Error. The number of calories and/or fat grams must be positive
>
> > Your food is low in fat.
> > The percentage of calories from fat in your food is % 0.0
>
> > It was supposed to print The calories or fat grams were incorrectly
> > entered since the calories from fat was greater then the total number of
> > calories.
>
> Boolean problem:
>
> if cal or fat <= 0
>
> That may be the way you say it or "think" it but it won't work.
>
> 'cal or fat' is evaluated first. Since they both have values this ALWAYS
> evaluates to 1 which is NEVER less than or equal to 0.
>
> You are looking for
>
> if (cal <= 0) or (fat <=0):
>
> (Note: Parenthesis not required, but it may help you understand precedence of
> evaluation. Also read here:
>
> http://www.ibiblio.org/g2swap/byteofpython/read/operator-precedence.html
>
> -Larry
that's the most incorrect thing i've heard all day!
if cal or fat <= 0 is parsed as if (cal) or (fat <= 0)
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