Re: reliability problem with Finance::QuoteHist::Yahoo

On 2008-07-14, smallpond <smallpond@xxxxxxxx> wrote:
Ted wrote:
I have been able to get this package to work sometimes. However,
invariably it fails on me part way through my script, after
downloading data for from one to four ticker symbols. The error is:

Can't use an undefined value as an ARRAY reference at C:/Perl/site/lib/
Finance/QuoteHist/Generic.pm line 863.

I have no information about how an undefined value is being passed
deep into the code of a package I didn't write. I took a quick look
into Generic.pm and yahoo.pm, but found no enlightenment so far
(there's a lot of code there).

Sometimes it arises when quotes() is executed, and at other times, it
occurs when dividends() is executed.
...

Without even looking at your code my guess is that Yahoo! is not particularly
pleased about providing an ad-sponsored service to web-scrapers. Part of the
reason that free services change their page format is to block people from
doing this. Yahoo! changes their page format fairly frequently and I'm willing
to bet that their web programmers have access to CPAN. If you need 7000 quotes
then its pretty clearly not for your personal portfolio. Maybe time for your
company to invest in a quote service.

If you have good software, configured to do intensive filtering, data
for 7000 tradables can be easily managable for an individual trader.
On the other hand, if an individual trader needs a reliable and accurate
data feed for automated analysis, a free yahoo service is probably a
poor choice.

It sounds like the package in question is not as robust as it could be,
allowing the user to encounter a run-time undefined value error instead
of producing a good error message. However, yahoo changing the server's
behavior or data format seems a likely initial cause of the problem.


--

.

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