TheWeatherApp < IoT_Course

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---+ The weather app
---++ Introduction

Several weather servers provide weather data and forecasts that can be used by a _weather app_. Here are the two I had a look into:
   * [[https://www.metaweather.com/][metaweather..com]]
   * [[https://openweathermap.org/][openweathermap.org]]
_openweathermap_ is probably the more powerful one but you must register (for free) to be able to use it, while you can get weather data from metaweather.com also without registration.

Both sites have their own API (<b>A</b>pplication <b>P</b>rogramming <b>I</b>nterface) and return the weather data in form of a json string, which must be decoded.Both sites provide a number of icons representing the different weather conditions.
---++ metaweather.com

In order to get weather data from<i> metaweather.com </i>you must perform an HTTP GET request on URL:

<verbatim>https://www.metaweather.com/api/location/{woeid}/</verbatim>

where _woeid_ is the "where on earth id", an integer number corresponding to the place for which you want the weather data. In order to get the <i>woeid </i>you can make a query giving the GPS coordinates of this place:

<verbatim>https://www.metaweather.com/api/location/search/?lattlong={latt},{long}</verbatim>

For my place in Austria the GPS data are
   * lattitude: 47.52637
   * longitude: 9.74882
and sending the request:

<verbatim>https://www.metaweather.com/api/location/search/?lattlong=47.53,9.75</verbatim>

returns:

<img alt="nearestCity.png" height="507" src="%ATTACHURL%/nearestCity.png" title="nearestCity.png" width="1119" />

This shows that the nearest city for which I can get a woeid is Zürich with the id:784794

Sending the request,using the method _reponse_ = _urequests.get(url)_ with the url below

<verbatim>https://www.metaweather.com/api/location/784794/</verbatim>

returns a json string of this type, from which you can pick the information of interest to you:

<img alt="weatherjson.png" src="%ATTACHURL%/weatherjson.png" title="weatherjson.png" />

_response.status_code_ gives you the http return code (should be 200 if successful).<br /><i>data = response.json()</i> gets the json data for you and converts it into a Python dictionary from which you must extract the information relevant to you. I pick up this information and put it into a friendly !GUI:

<img alt="metaweather.png" src="%ATTACHURL%/metaweather.png" title="metaweather.png" />

If you compare this with the json string, you should find back the information. Only the wind speed is different because I convert the units from mph to kph. You can also see that it is really cold here in Switzerland in February!
---++ openweathermap.org

The basic way for getting weather data from openweathermap.org is the same as described above. However the url string is different following a different API. On openweathermap.org you don't need the woeid, but you can use a city name or the GPS data directly. On the other hand you need an extra apikey, which you get with your registration.

-- %USERSIG{UliRaich - 2021-02-07}%

---++ Comments

%COMMENT%

Attachments

Topic attachments
I	Attachment	History	Action	Size	Date	Who
png	metaweather.png	r1	manage	101.0 K	2021-02-13 - 10:02	UliRaich
png	metaweather_app.png	r1	manage	16.0 K	2021-02-08 - 20:18	UliRaich
png	nearestCity.png	r1	manage	66.7 K	2021-02-07 - 13:45	UliRaich
png	weatherjson.png	r2 r1	manage	118.9 K	2021-02-13 - 10:08	UliRaich

Topic revision: r4 - 2021-02-18 - UliRaich