member thudfoo wrote:
On 4/24/08, Jonathan Gardner <[EMAIL PROTECTED]> wrote:
On Apr 24, 5:28 am, malkarouri <[EMAIL PROTECTED]> wrote:
>
> What's wrong with raising ZeroDivisionError (not stopping the
> exception in the first place)?
>
Because when I use your module, call avg (or mean) without args, I
should see an error that says, "Hey, you have to pass at least one
value in!"
ZeroDivisonError doesn't mean that. It means I tried to divide by
zero. Naively, I don't see where I was dividing by zero (because I
don't remember how to calculate the mean---that's what your code was
for.)
ValueError does mean that I didn't pass the right kind of arguments
in. ValueError("No items specified") would be even clearer. (Or maybe
TypeError?)
In general, any exception thrown should be meaningful to the code you
are throwing it to. That means they aren't familiar with how your code
works.
[source]|557> def average(n, *ints):
|...> return (sum(ints)+n) / (len(ints) + 1)
|...>
[source]|558> average (1,2,3)
<558> 2
[source]|559> average(3)
<559> 3
[source]|560> average(1,2)
<560> 1
[source]|561> average(0)
<561> 0
[source]|562> average()
---------------------------------------------------------------------------
TypeError Traceback (most recent call last)
/usr/share/doc/packages/python-dateutil/source/<ipython console> in <module>()
TypeError: average() takes at least 1 argument (0 given)
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It would also be usual to use floating arithmetic to ensure that the
mean of 1 and 2 was 1.5 rather than 1.
regards
Steve
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