openweathermap

weather.py

# This code has been tested with Python 3.11.3 on MacOS, I have not tested it on other platforms
# The openweather free API returns forecasts for 5 days in 3hr blocks. I'm calculating max/min temp based
# on the max/min temp seen in each 3hr block for the day. 
# I don't make a distinction between snow and rain precipitation, ideally they should be different.  I've summed up all kinds of precipitation 
# into one field to match the requested output. 
# TODO: 
# Only US zipcodes are supported and validated, the API supports other countries but I have not had time to test
# Needs more tests


import os
import sys
import urllib.request
import json
import re



# rudimentary check for valid US zip code
def valid_input(zipcode):
    return re.match('^[0-9]{5}(?:-[0-9]{4})?$', zipcode)


# Api returns kelvin, convert to F
def k_to_f(k):
    f = (k - 273.15) * 1.8 + 32
    return f

# Convert to US date which is 
# Month-Day-Year, unlike the rest of the world :( 
def us_date(date):
    out = date.split('-')
    return '-'.join([out[1], out[2], out[0]])

# We're iterating over the output and creating the display dict which will what we want to show
def display(out):
    display = {}
    for t in out['list']:
        # Gets us year-month-day
        d = t['dt_txt'].split(' ')[0]
        # Check if we have readings for this day
        j = display.get(d)
        if j is None:
            # Add an entry for the day, with the max/min temp set and precipitation set to zero
            j = display[d] = [t['main']['temp_max'], t['main']['temp_min'], 0]
        if t['main']['temp_max'] > j[0]:
            display[d][0] = t['main']['temp_max']
        if t['main']['temp_min'] < j[1]:
            display[d][1] = t['main']['temp_min']
        # chances of precipitation, could be rain or snow!
        precip = 0
        if t['pop'] > 0:
            rain = t.get('rain')
            snow = t.get('snow')
            if rain is not None:
                precip = precip + rain.get('3h')
            if snow is not None:
                precip = precip + snow.get('3h')
            display[d][2] = display[d][2] + precip
    return display

def fetch_weather():
    api_key = os.getenv('API_KEY')
    if api_key is None:
        print('Please set an OpenWeatherMap API key env variable API_KEY')
        sys.exit(1)
    inp = input('Enter a zip code. Example - 90210: ')
    inp = inp.rstrip()
    if valid_input(inp) is None:
        print('Please provide a valid US zipcode (more formats coming soon)')
        sys.exit(1)

    api_endpoint = f'https://api.openweathermap.org/data/2.5/forecast?zip={inp}&appid={api_key}'
    try: 
        f = urllib.request.urlopen(api_endpoint)
        out = json.loads(f.read().decode('utf-8'))
    except urllib.error.HTTPError as e:
        print(f'failed with {e.code}, {e.reason}')
        sys.exit(1)
    return out


if __name__ == '__main__':
    out = fetch_weather()
    p = display(out)
    print('# Date\t\tTemperature\tPrecipitation')
    for k in p:
        # Format as US date which is month-day-year
        d = us_date(k)
        # Get the list that contains the temp and precipitation
        v = p[k]
        # Convert to Fahrenheit from Kelvin, only need .2f precision
        min = "{:.2f}".format(k_to_f(v[0]))
        max = "{:.2f}".format(k_to_f(v[1]))
        precip = "{:.2f}".format(v[2])
        print(f'# {d}\t{min}/{max}\t\t{precip}')