pymetar - a module to fetch and parse METAR reports
---------------------------------------------------

NOTE: If you're looking for information regarding Python 3 and
pymetar, see the end of this document.

The National Oceanic and Atmospheric Administration (NOAA,
www.noaa.gov) provides easy access to the weather reports
generated by a large number of weather stations (mostly at
airports) worldwide. Those reports are called METAR reports and
are delivered as plain text files that look like this:

Duesseldorf, Germany (EDDL) 51-18N 006-46E 41M
Jul 26, 2002 - 03:50 AM EST / 2002.07.26 0850 UTC
Wind: from the SW (220 degrees) at 9 MPH (8 KT):0
Visibility: 3 mile(s):0
Sky conditions: mostly cloudy
Weather: mist
Temperature: 60 F (16 C)
Dew Point: 57 F (14 C)
Relative Humidity: 87%
Pressure (altimeter): 30.00 in. Hg (1016 hPa)
ob: EDDL 260850Z 22008KT 5000 BR SCT006 BKN012 16/14 Q1016 BECMG BKN015
cycle: 9

While this is convenient if you just want to quickly look up the
data, there's some effort involved in parsing all of this into a
format that is digestible by a program. Plus, you have to remember
the base URL of the reports and fetch the file.

This is what this library does. All you have to do is find the
station you're interested in at
http://www.nws.noaa.gov/tg/siteloc.shtml and feed the 4-letter
station code to the MetarReport class.

On the user end, the library provides a large number of methods to
fetch the parsed information in a plethora of formats. Those
functions are described in the file librarydoc.txt which was in
turn generated using PyDoc.

As of version 0.5, pymetar uses urllib2 which in turn makes it
easy to honor the environment variable HTTP_PROXY. This simplifies
use of a proxy tremendously. Thanks go to Davide Di Blasi for both
suggesting and implementing this. The environment variable is easy
to use: just set it to:

http://username:password@proxy.yourdomain.com:port 

As of version 0.11, you can also specify a proxy (with the same
syntax) as an argument to the fetching function. This is sometimes
easier when using PyMETAR in a web application environment (such
as ZopeWeatherApplet by Jerome Alet). See librarydoc.txt for
details on how to accomplish that. 

You can also use IPs instead of hostnames, of course. When in
doubt, ask your proxy admin.

Due to some peculiarities in the METAR format, I can not rule out
the possibility that the library barfs on some less common types
of reports. If you encounter such a report, please save it and the
error messages you get as completely as possible and send them to
me at klausman-pymetar@schwarzvogel.de - Thanks a lot!

Of course you may send all the other bugs you encounter to me,
too. As this is a Python library, chances are that you are Python
programmer and can provide a patch. If you do so, please, by all
means use Spaces for indentation, four per level, that makes
merging the patch a lot easier.

Python 3
--------

Pymetar does currently not support Python 3 (Python 2.4-2.7 should
be fine. Versions <2.4 are not officially supported but may work
by chance).

I'm currently in the process of plotting out the future of
Pymetar, which naturally includes thinking about Py3. The design
of the whole library is now close to eight years old. At this
point, there is little that I can do in the ways of changing the
API gradually, so I'm thinking about releasing a totally
incompatible new library which will only share the basic purpose of
Pymetar. I don't think that the current code can be refactored
easily and I have meant to try different approaches to the same
problem (pylex, dispatcher code, state machines and sundry other
stuff). *If* I go that route, it will be Py3-only, since that is
the future. Also, I will create a better test suite/scaffolding.

If you want to join me in building and designing the "new
Pymetar", feel free to join me on the mailing list.

Oh, and we need a new name or some other distinctive tag for the
new code. And no, it will not be pymetar-ng.
