From: rwob...@hotmail.com
To: tutor@python.org
Date: Fri, 10 Sep 2010 16:12:08 +0000
Subject: Re: [Tutor] exceptions problem
Date: Fri, 10 Sep 2010 18:07:13 +0200
From: f...@libero.it
To: tutor@python.org
Subject: Re: [Tutor] exceptions problem
Oops, I sent this to Roelof... Ok, I must amend it anyway...
On 10/09/2010 17.13, Roelof Wobben wrote:
> ...
> def readposint():
> x = raw_input("Please enter a positive integer :")
> try:
> x = int(x) and x> 0
> 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 the x> 10 is never checked.
>
> Must I use two try except now ?
Your first problem has nothing to do with exception handling.
The culprit is Line 4:
> x = int(x) and x> 0
I suppose that you forgot a second equal sign between x and int(x). If
it were
> x == int(x) and x > 0
it would have worked as expected. But this would not trigger any
exception, if X is a number. So let's add one:
> if not (x == int(x) and x > 0): raise(ValueError)
Hope that helps,
> Roelof
FrancescoHello Francesco,I change it to this :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 Truey = readposint()
print y
while y == False:
readposint()
print "You have entered : ", yBut -9 and 2 are both true.RoelofBecause I want
to understand why this happens I wrote this test programm :def readposint():
x = raw_input("Please enter a positive integer :")
print x
if x == int(x) :
print "01-True"
else:
print "01-False"
print int(x)
if x > 0 :
print "02-True"
else:
print "02-False"
return y = readposint()
print y
while y == False:
readposint()
print "You have entered : ", y But I see wierd output :When x = 3 I get this
output :Please enter a positive integer :3301-False302-TrueNoneYou have entered
: None
That's wierd. 3 is a integer so 01 must be True and 3 is bigger then 0 so that
one must be false.
Can someone explain me why this happens ?
Roelof
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