Sample Python script to use with the Hello World Code4Lib code club

weather-int.py

# weather-int.py - get average temperature data from the World Bank ClimateWeb API
# 
# Usage: python weather-int.py XXX      where XXX is a ISO 3-letter country code
#                                       e.g. CAN, USA, GBR
#
# Collectively written during the Feb 5-6 Software Carpentry workshop
# at the University of Toronto iSchool.
# https://swcarpentry.github.io/2015-02-05-toronto
# Edited by Thomas Guignard <tom@timtom.ca> for the Code4Lib Monday Night code club
# Version: March 30, 2015


# Import libraries
import urllib   # Useful to process web queries
import csv      # To process CSV data (comma-separated values)
import sys      # To interact with the OS, in this case to get command-line arguments


# Define base URL for getting data. {0} is place holder for 3-letter country code
URL = 'http://climatedataapi.worldbank.org/climateweb' + \
      '/rest/v1/country/cru/tas/year/{0}.csv'


# Define function get_data
# Usage: get_data(<XXX>)    where XXX is a string containing a 3-letter country code
def get_data(where):
    # format the URL by replacing the place holder with the 3-letter country code
    actual = URL.format(where)
    # get the CSV data from the formatted URL
    raw = urllib.urlopen(actual)
    # skip the first line of the CSV file, as it contains headers
    header = raw.readline()
    # run the CSV data through the csv.reader function
    cooked = csv.reader(raw)
    # init values
    total = 0.0
    num_seen = 0
    # loop through all lines in the CSV file
    for line in cooked:
        # the first column contains the year
        year = int(line[0])
        # the second column contains the average temperature for that year
        temp = float(line[1])
        # add this year's temperature to the total so far
        total = total + temp
        # increment the number of readings
        num_seen = num_seen + 1
    # once the loop has run, compute simple average
    # first, check if we have at least one value to average
    if num_seen > 0:
        # compute simple average
        ave_temp = total / num_seen
        # print the 3-letter country code and the computed average on stdout
        print '{0},{1}'.format(where, ave_temp)
    else:
        # if there are no values to average, throw an error of type "Warning"
        raise Warning('EmptyCountryFile')


# This is the main code body
# load the provided arguments into the countries array (more than one country can be provided)
# (arguments are not checked for validtiy, valid 3-letter codes are assumed)                                       
countries = sys.argv[1:]
# print a line containing headers for returned values on stdout
print 'country,ave surface temp (C)'
# loop through the arguments array
for country in countries:
    # for each country, run the get_data() function
    # exceptions are use to avoid breaking the program if one country code is invalid
    try:
        get_data(country)
    # if one of the country codes is invalid, print a line with a value of NULL
    except Warning:
        print '{0},NULL'.format(country)
        

# END