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Help please

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  Help please khaosyt@gmail.com - 2013-03-31 22:15 -0700
    Re: Help please Chris Angelico <rosuav@gmail.com> - 2013-04-01 16:24 +1100
      Re: Help please khaosyt@gmail.com - 2013-03-31 22:41 -0700
        Re: Help please Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2013-04-02 00:09 +0000
      Re: Help please khaosyt@gmail.com - 2013-03-31 22:41 -0700

#42441 — Help please

I want to add up the integers of this code in one line. For example, if I had the code

integer = 0
denom = 10
again = "y" #sentinel:
while again == "y" or again == "Y":
    integer = input("Enter a positive integer: ")
    while denom <= integer:
        denom = denom*10
    while denom > 1:
        denom = denom/10
        number = integer/denom
        integer = integer%denom
        print str(number)
    again = raw_input("Again? (Y/N): ")

and inputted "54321," it would look like:
Enter a positive integer: 54321
5
4
3
2
1
Again? (Y/N): n

What I want to do is add up the "54321" so it comes out with
"Sum of digits is 15." on one line.

Thanks!

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#42442

On Mon, Apr 1, 2013 at 4:15 PM,  <khaosyt@gmail.com> wrote:
>     integer = input("Enter a positive integer: ")
>     again = raw_input("Again? (Y/N): ")

Okay, the first thing I'm going to say is: Don't use input() in Python
2. It's dangerous in ways you won't realize. Use int(raw_input(...))
for something like this, which will guarantee you an integer.

I'm guessing this is homework. Please be honest about that; we'll help
you learn but won't just give you the answers.

All you need to do is initialize something to zero, and then keep
adding 'number' onto it in the loop. You should be able to sort that
out.

ChrisA

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#42444

On Monday, April 1, 2013 1:24:52 AM UTC-4, Chris Angelico wrote:
> On Mon, Apr 1, 2013 at 4:15 PM,  <khaosyt@gmail.com> wrote:
> 
> >     integer = input("Enter a positive integer: ")
> 
> >     again = raw_input("Again? (Y/N): ")
> 
> 
> 
> Okay, the first thing I'm going to say is: Don't use input() in Python
> 
> 2. It's dangerous in ways you won't realize. Use int(raw_input(...))
> 
> for something like this, which will guarantee you an integer.
> 
> 
> 
> I'm guessing this is homework. Please be honest about that; we'll help
> 
> you learn but won't just give you the answers.
> 
> 
> 
> All you need to do is initialize something to zero, and then keep
> 
> adding 'number' onto it in the loop. You should be able to sort that
> 
> out.
> 
> 
> 
> ChrisA

Elaborate, please.

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#42530

On Sun, 31 Mar 2013 22:41:32 -0700, khaosyt wrote:

> On Monday, April 1, 2013 1:24:52 AM UTC-4, Chris Angelico wrote:
>> On Mon, Apr 1, 2013 at 4:15 PM,  <khaosyt@gmail.com> wrote:
>> 
>> >     integer = input("Enter a positive integer: ")
>> 
>> >     again = raw_input("Again? (Y/N): ")
>> 
>> 
>> 
>> Okay, the first thing I'm going to say is: Don't use input() in Python
>> 
>> 2. It's dangerous in ways you won't realize. Use int(raw_input(...))

[...]

> Elaborate, please.


The input() function takes the user's text, and automatically evaluates 
it as if it were code. In the hands of a non-expert, that can lead to 
some unexpected errors:

py> answer = input("what is your name? ")
what is your name? Steve
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "<string>", line 1, in <module>
NameError: name 'Steve' is not defined



But at least that gives you an error. It can also give you weird and 
unexpected results. Suppose my name was Lenny, and I did this:

py> answer = input("what is your name? ")
what is your name? len
py> print answer
<built-in function len>



Worse, because input evaluates text as code, it can do anything, 
including bad things:

py> answer = input("what is your name? ")
what is your name? 200**300**300
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "<string>", line 1, in <module>
MemoryError


(while the above code was running, my computer got slower and slower and 
slower, and potentially it could have locked up completely).


So the general advice is, treat the input() function as For Experts Only, 
and always use raw_input() instead.




-- 
Steven

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#42445

On Monday, April 1, 2013 1:24:52 AM UTC-4, Chris Angelico wrote:
> On Mon, Apr 1, 2013 at 4:15 PM,  <khaosyt@gmail.com> wrote:
> 
> >     integer = input("Enter a positive integer: ")
> 
> >     again = raw_input("Again? (Y/N): ")
> 
> 
> 
> Okay, the first thing I'm going to say is: Don't use input() in Python
> 
> 2. It's dangerous in ways you won't realize. Use int(raw_input(...))
> 
> for something like this, which will guarantee you an integer.
> 
> 
> 
> I'm guessing this is homework. Please be honest about that; we'll help
> 
> you learn but won't just give you the answers.
> 
> 
> 
> All you need to do is initialize something to zero, and then keep
> 
> adding 'number' onto it in the loop. You should be able to sort that
> 
> out.
> 
> 
> 
> ChrisA

Elaborate, please.

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