SenseHAT weather forecaster

Here’s a really simple scrolling weather forecast for the RaspberryPi SenseHAT.

It uses the BBC Weather RSS feed, so you would replace the postcode (‘bs1′) with your own to get your local forecast.

You’ll also need to install feedparser – this is very easy. Just type
sudo pip install feedparser
on the Raspberry Pi command line, and you should be good to go. Obviously, your Pi needs to be connected to the internet for this to work.

Here’s the simplest possible version of the Python code to display a 3 day forecast in rolling text:

import feedparser
from sense_hat import SenseHat

sense = SenseHat()

d = feedparser.parse('http://open.live.bbc.co.uk/weather/feeds/en/sw1/3dayforecast.rss')
entries = int(len(d['entries']))
for x in range(entries):
    sense.show_message(d['entries'][x]['title'])

This reads the RSS feed’s XML into an array called ‘d’. It then counts how many forecasts there are – I guess there will always be 3, but seeing as it’s easy to count them, let’s count them anyway. It then loops 3 times showing the forecast for that day, which is stored in the ‘title’ block of the XML.

A few possible improvements spring to mind.

It’s quite a long scrolling message, so let’s add different colours for each day of the week, so when you glance at it you know if it’s today’s weather (white text), tomorrow’s (green) or the day after tomorrow (blue):

import feedparser
from sense_hat import SenseHat

sense = SenseHat()
colours = [[255,255,255],[0,255,0],[0,0,255]]

print colours

d = feedparser.parse('http://open.live.bbc.co.uk/weather/feeds/en/bs1/3dayforecast.rss')
entries = int(len(d['entries']))
for x in range(entries):
    sense.show_message(d['entries'][x]['title'], text_colour=colours[x])

(If you did have more than 3 entries in a 3-day forecast, the code would break – you’d need to add more colours).

Now I see the SenseHAT can’t display degree signs, it shows a question mark instead, so let’s strip them out:

import feedparser
from sense_hat import SenseHat

sense = SenseHat()
colours = [[255,255,255],[0,255,0],[0,0,255]]

d = feedparser.parse('http://open.live.bbc.co.uk/weather/feeds/en/bs1/3dayforecast.rss')
entries = int(len(d['entries']))
for x in range(entries):
    wx = (d['entries'][x]['title'])
    disp_wx = wx.replace(u"\u00B0",'')
    sense.show_message(disp_wx, text_colour=colours[x])

I’ve used \u00B0 as this is the escape sequence for a degree symbol, and I replace this with nothing, though you could replace it with the word ‘degrees’.

So far, this only runs once, so let’s get the program to keep running. Because we are responsible digital citizens, we won’t keep requesting the weather forecast every few seconds, we’ll ask for it once when we start the program running, and then keep the text scrolling by adding a while True statement:

import feedparser
from sense_hat import SenseHat

sense = SenseHat()
colours = [[255,255,255],[0,255,0],[0,0,255]]

d = feedparser.parse('http://open.live.bbc.co.uk/weather/feeds/en/bs1/3dayforecast.rss')
entries = int(len(d['entries']))

while True:
    for x in range(entries):
        wx = (d['entries'][x]['title'])
        disp_wx = wx.replace(u"\u00B0",'')
        sense.show_message(disp_wx, text_colour=colours[x])

Next I notice that ‘maximum/minimum temperature’ is a bit of a screenful, so let’s change that to ‘high’ or ‘low’:

import feedparser
from sense_hat import SenseHat

sense = SenseHat()
colours = [[255,255,255],[0,255,0],[0,0,255]]

d = feedparser.parse('http://open.live.bbc.co.uk/weather/feeds/en/bs1/3dayforecast.rss')
entries = int(len(d['entries']))

while True:
    for x in range(entries):
        wx = (d['entries'][x]['title'])
        disp_wx = wx.replace(u"\u00B0",'')
        disp_wx = disp_wx.replace('Maximum Temperature','High')
        disp_wx = disp_wx.replace('Minimum Temperature','Low')
        sense.show_message(disp_wx, text_colour=colours[x])

Finally, this version strips out the Fahrenheit and gets a fresh forecast after displaying the 3 day forecast 10 times:

import feedparser
from sense_hat import SenseHat
import re

sense = SenseHat()
colours = [[255,255,255],[0,255,0],[0,0,255]]

def fetch_weather():
    w = feedparser.parse('http://open.live.bbc.co.uk/weather/feeds/en/bs1/3dayforecast.rss')
    return(w)

d = fetch_weather()
entries = int(len(d['entries']))

counter = 0

while True:
    counter = counter + 1
    for x in range(entries):
        wx = (d['entries'][x]['title'])
        disp_wx = wx.replace(u"\u00B0",'')
        disp_wx = disp_wx.replace('Maximum Temperature','High')
        disp_wx = disp_wx.replace('Minimum Temperature','Low')
        disp_wx = re.sub(r'\([^)]*\)', '', disp_wx)
        sense.show_message(disp_wx, text_colour=colours[x])
    if counter == 10:
        d = fetch_weather()
        entries = int(len(d['entries']))
        sense.show_message('UPDATING', text_colour=[255,0,0])
        counter = 0

A nice extension would be to display symbols based on the weather, or perhaps change text colour depending on the temperature – red if it’s warm, blue if it’s cold? The sky (ahem) is the limit…