I’m embarrassed I put this off so long. I must have sat down to do it half a dozen times. I think this means I found it hard. I think I felt like I suddenly didn’t know anything well enough to write tests, but it was easier once I got started. In fact, I think I may have got carried away…
*1. A question to discriminate beginners from competent practitioners.
*Which of the following most accurately describes a server-side web API?
A. It’s a programmatic interface to a web-based service, accessed via HTTP.
B. It’s a programmatic interface to a web browser’s functionality, usually via JavaScript.
C. It’s a set of options you can select on a web site, accessed via HTML.
D. It’s a set of options you can select in web server software, usually via httpd.conf.
*2. An exercise to improve skill.
*Complete the following code to print the exchange rate for Canadian dollars. Read the comments carefully. Notice that there are two parts to the question.
from urllib2 import urlopen
from urllib import urlencode
import json
# Provide the URL.
url = 'http://query.yahooapis.com/v1/public/yql'
# We pass our request to the web API as a query string.
# Don't build query strings as strings, build them as dicts.
params = {'q': 'select Rate from yahoo.finance.xchange where pair in ("CAD")',
'env': 'http://datatables.org/alltables.env',
'format': 'json'
}
# A dict is easily converted to an HTTP-safe query string.
query = urlencode(params)
# Opened URLs are file-like. You can't use 'with... as'.
# We'll construct the URL+query string ourselves, rather
# than passing them separately, to force urllib2 to use GET.
full_url = '{0}?{1}'.format(url, query)
f = urlopen(full_url)
# QUESTION 2a: The web API is 'open', complete the line to read it:
r =
# The result is a JSON string; a dict is more useful.
result = json.loads(r)
# QUESTION 2b: Complete the line to retrieve the rate as a float.
rate =
*3. A question to assess the improvement.
*Here is a web API query:
url = 'http://ajax.googleapis.com/ajax/services/search/web' query = 'v=1.0&q=how+do+i+convert+ft+to+m' f = urllib2.urlopen(url, query)
What is the most likely outcome?
A. Success: '{"responseData": {"results":[{"GsearchResultClass":..., etc.
B. Error: '{"responseData": null, "responseDetails": "invalid version", "responseStatus": 400}'
C. Error: HTTPError: HTTP Error 400: Bad Request
D. Error: HTTPError: HTTP Error 405: HTTP method POST is not supported by this URL