Re: [Tutor] exceptions problem

[Francesco Loffredo]

On 10/09/2010 18.12, Roelof Wobben wrote:
...
def readposint():
        x = raw_input("Please enter a positive integer :")
        try:
              if not (x == int(x) and x<  0): raise(ValueError)
        except:
                print x , "is not a positive integer.    Try again."
                return False
        return True
y = readposint()
print y
while y == False:
        readposint()
print "You have entered : ", y

But -9 and 2 are both true.
My fault, I didn't notice that after raw_input, whatever you enter is a 
STRING, not an integer! So, without any exception thrown, the comparison
x == int(x) is always False. Let's make it better:
   if (int(x)<0 or (float(x) - int(x) > 0)): raise(ValueError)


Then, if the input value x is indeed a positive integer, you should 
return x, not True or False. Try returning -1 if the exception is 
thrown, in line 7, and returning x in line 8. Then, you should change 
also line 12... ok, here's to you:

def readposint():
    x = raw_input("Please enter a positive integer :")
    try:
        if (int(x)<0 or (float(x) - int(x) > 0)): raise(ValueError)
    except:
        print x , "is not a positive integer.    Try again."
        return -1
    return x

y = readposint()
print y
while y == -1:
    readposint()
print "You have entered : ", y


Roelof
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09/09/10 08:34:00
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