1. Intro to Web Services
Consuming the Web

2. Introduction to Web Clients
We've seen how to write server-side web applications
Today's focus: Web Clients
A web client is a program that interacts with a server-side web application called a web service
A web service is a server-side web application that is designed to be accessed by programs rather than humans

3. Meet the requests module
Third-party Python module for downloading web pages
Install:
pip install requests
Use:
import requests
response = requests.get('
print(response.text)
requests Documentation:

4. Requests API The get() method returns a Response object Properties:
response = requests.get('
Properties:
status_code
200 – ok
404 – not found
text (downloaded data)
Methods:
json()

5. Downloading Data Websites publish data in different formats
HTML
Media files
CSV
XML
JSON
Use the requests module to download any type of data
Not just web pages

6. Downloading CSV Data Hartford fire data in CSV format
Process with csv reader
response = requests.get('
lines = response.text.split('\n')
reader = csv.reader(lines[1:])
for line in reader:
alm_time = line[2]
arv_time = line[4]
print(alm_time, arv_time)

7. JSON

8. JSON Common data interchange format More powerful/flexible than CSV
Example:
{"menu": {
"value": "File",
"popup": {
"menuitem": [
{"value": "New", "onclick": "CreateNewDoc()"},
{"value": "Open", "onclick": "OpenDoc()"}, ] } }}

9. Parsing JSON Use json module (built-in)
json.loads() function converts a string containing JSON to a Python list/dictionary
See examples/dictionaries_csv/fires.py

10. Downloading JSON Data
requests module has built-in support for parsing JSON
See examples/dictionaries_csv/fireswebservice.py

11. Web Services

12. Hartford Fire Data Consider this URL:
We can control the downloaded data via a query parameter
What does that tell you about the nature of this URL?
Static vs. Dynamic?

13. API
Recall: An interface is the boundary between a client and a mechanism used by the client
Input flows from the client through the interface to the mechanism
Output flows from the mechanism through the interface back to the client
API: "Application Program Interface"
Python API = Function interfaces + Documentation
Example: requests API, file API, string API

14. Web API Web applications get their input via
URL
Query strings
Submitted form data
Cookies
A web service provides a web API that specifies format of URL and query strings that control what data is downloaded

15. Hartford Fire Data Web API