lab-17.md

@@ -10,6 +10,8 @@ apis
 
 # step 0: consuming apis
 
+_note that step-0 has been updated to reflect changes in urllib in python 3_
+
 ## using the OpenWeatherMap api
 
 * to use the open weather map, sign up at http://openweathermap.org/appid
@@ -26,13 +28,17 @@ apis
 		url = "http://api.openweathermap.org/data/2.5/weather?q=London%2C%20UK&units=metric&appid=<YOUR API KEY HERE>"
 
 * note the location "London, UK" is url encoded in the url string
-* import the urllib2 library so you can request the url
+* import urlopen from urllib.request so you can request the url (see https://docs.python.org/dev/tutorial/stdlib.html#internet-access)
 
-		import urllib2
+		from urllib.request import urlopen
 
 * read the data returned by the url
 
-		data = urllib2.urlopen(url).read()
+		data = urlopen(url).read()
+
+* note that python is making an http request so the data is returned as binary data; to use it we need to decode it according to the charset returned by the server (which will usually be utf-8)
+
+		data = data.decode(data.headers.get_content_charset())
 
 ## parsing the data
 
@@ -49,7 +55,7 @@ apis
 
 * we want to check the structure of this data, so we can 'pretty print' the json data using json.dumps
 
-		print json.dumps(weather, indent=4, sort_keys=True)
+		print(json.dumps(weather, indent=4, sort_keys=True))
 
 ## accesssing the data
 
@@ -81,11 +87,9 @@ apis
 * remember from step 0 that the most common format for returning api data is json
 * we will create a simple api for our mytwits flask app using a flask function called jsonify http://flask.pocoo.org/docs/0.12/api/#flask.json.jsonify
 * this will directly return your json structure to the browser
-* you will need to import jsonify at the top of your app i.e.
-
-        from flask import jsonify
-
-
+* to use jsonify you will need to import it i.e.	
+		
+		from flask import jsonify
 
 ## db -> api 
 
@@ -128,7 +132,7 @@ apis
 
 
 
-# using flask-restful
+# step 2: using flask-restful
 
 * now we'll create a fulled-specced api using the flask-restful extension https://flask-restful.readthedocs.io/en/latest/
 * this requires a bit more set up but rewards us with more powerful functionality that handles the full range of RESTful HTTP methods
@@ -162,6 +166,33 @@ apis
 
 		api.add_resource(TwitsApi,'/api')
 
+## no jsonify, just dictionaries
+
+flask-restful will deal with converting the data to json and adding the correct headers, so we don't need to use jsonify.
+
+however, to take advantage of flask-restful we need to pass it our data in the form of dictionaries. in our previous use of pymysql in mytwits_mysql.py we used the default cursor which returns the results as tuples. however, we can force pymysql to return the sql results as a python dictionary using pymysql.cursors.DictCursor (see the bottom of the pymysql api ref on cursors https://pymysql.readthedocs.io/en/latest/modules/cursors.html).
+
+so for queries that we want to pass back to the api we replace 
+
+        with self.db.cursor() as cursor:
+
+with 
+
+        with self.db.cursor(pymysql.cursors.DictCursor) as cursor:
+
+(
+Note that this also means tweaking our jinja templates for the html output, where we will need to replace 
+
+	  <div class="col-md-4">{{ twit[0] }}</div>
+		
+
+with
+
+	<div class="col-md-4">{{ twit['username'] }}</div>
+
+)
+
+
 
 ## data formatting and argument parsing