Thanks for the reply Alan and Noah, I really appreciate the help. I am really
trying to understand this although still cannot seem to grasp it all. I have
modified my program although now it seems to be giving me the wrong answer with
the correct answer when I input any value.
I have program:
model=raw_input("What kind of car do you drive?")
gallons=raw_input("How many gallons have you driven?")
number1 = float (gallons)
miles=raw_input("How many miles have you driven?")
number2 = float (miles)
try:
model=float(model)
except ValueError:
print "I cannot compute your total miles to gallon with those values."
else:
print "Your average number of miles to gallons is",
print number1 / number2
Output:
What kind of car do you drive?fire
How many gallons have you driven?10
How many miles have you driven?5
I cannot compute your total miles to gallon with those values.
On Apr 27, 2011, at 10:02 AM, Alan Gauld wrote:
>
> "Johnson Tran" <aznj...@me.com> wrote
>
>> I started out with a short program below and I thought it was working
>> although I cannot seem to figure out how to use the except ValueError so
>> that when the user puts an invalid answer the program does not read with an
>> error.
>
> You have to replace the line that says 'pass' with code that does something
> to make the value correct. Asking the user to try again with a more sensible
> value would be a start.
>
>> Although according to the error message, it seems to be saying that my line
>> 4 "number1 = float (number_string1)" is incorrect.
>
> Its not saying its incorrect, its saying thats where the ValueError occured.
> Which is true because you entered 'test' which cannot be converted to a float
> - its an invalid value.
>
>> model=raw_input("What kind of car do you drive?")
>> number_string1=raw_input("How many gallons have you driven?")
>> number1 = float (number_string1)
>> number_string2=raw_input("How many miles have you driven?")
>> number2 = float (number_string2)
>
> You will fin it easier if you use descriptive names for your variables.
>
> gallons and miles
> would seem reasonable here...
>
>> try:
>> model=float(model)
>> except ValueError:
>> pass
>
> This says if you get an error ignore it (ie pass).
> But you don't want to ignore it, you want to get a valid value.
>
>> print "Your average number of miles to gallons is",
>> print number1 / number2
>
> HTH,
>
>
> --
> Alan Gauld
> Author of the Learn to Program web site
> http://www.alan-g.me.uk/
>
>
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