Begginers Guide - Exrcise. Help me, plz!

[Bengt Richter]

On Fri, 22 Mar 2002 10:38:22 -0800, Jeff Shannon <jeff at ccvcorp.com> wrote:

>
>
>Jim Dennis wrote:
>
>>  Shouldn't all these (helpful) examples be using raw_input() rather
>>  than input().  Do we really want the new user to be implicitly and
>>  blindly using eval(raw_input())?
>
>Yes, they should.  :)  The calls to input() should, in this case, all be
>replaced by int(raw_input()), and optionally wrapped in a try/except and while
>loop, so that the program can prompt again if a non-numeric value is given.  I
>almost mentioned this in my earlier response, but decided not to overly confuse
>the O.P. -- this essentially doubles the code size.
>
>while sum < sum_stop:
>    num = None
>    while num is None:
>        try:
>            num = int(raw_input("Please enter the number:"))
>        except ValueError:
>            print "That's not a number.  Try again!"
>    sum = sum + num    # could also be  sum += num
>    print "The sum is", sum
>print "and it is > 100"
>
>Alternatively, instead of setting num to None and watching for that to change,
>we could use a 'while 1:  try: ...  except: ... else: break'  structure.
>
Alternatively again, we could factor out the function of getting a number, to
keep that concept bite sized (and also changing a few details ;-)  e.g.:


---<snip>---
def get_num():
    while 1:
        try:
            return int(raw_input("Please enter an integer: "))
        except ValueError:
            print "That's not a integer.  Try again!"

sum = 0; sum_stop = 100
while sum < sum_stop:
    sum += get_num()
    print "The sum is", sum

print "... and it is >= %d" % sum_stop
---<snip>---

Please enter an integer: 2.
That's not a integer.  Try again!
Please enter an integer: 2
The sum is 2
Please enter an integer: -5
The sum is -3
Please enter an integer: 99
The sum is 96
Please enter an integer: 3
The sum is 99
Please enter an integer: 1
The sum is 100
... and it is >= 100

Regards,
Bengt Richter