CS 1112: Spring 2020

Class 14 — Friday February 14

Web chrestomathics

How was I to know — Person sitting next to me — Would become my spouse

Look both ways

Back or ahead

Agenda

Web access and analysis

Foreshadow programmer-defined functions

Notices

Happy Valentine's day to you all

No office yours today

For the fun of it

Reveal one of your super power(s).

Share a selfie.

To do list

Review class artifacts.

Do homework.

Prepare for Test 1

Downloads

Program master_plan.py

Program secret_revealed.py

Program paging_page.py

Program get_a_dataset.py

Module url.py

CS 1112 CSV datasets

Primary examples

Web programming

The acronym URL stands for Uniform Resource Locator. Think of a URL as an address. Everything on the WWW has its own unique URL.

Our introduction to interacting with the web is intentionally simple. Industrial-strength web applications also require familiarity with other and more powerful URL modules.

To start off the only thing we need is access to the module urllib.request. The module supports working with URLs.

import urllib.request

The module has a function urllib.request.urlopen() that returns a connector to a URL resource (think web page). Sample usage:

stream = urllib.request.urlopen( link )

Although we do not care in itself, the value returned by urlopen() is an http.client.HTTPResponse object. What we do care is that such an object has a function read() that can be used to get the contents of the web resource to which it is connected.

page = stream.read()

The contents provided by read() is a string encoded in a web format rather than as regular text.

Besides having functions lower() and upper(), a string also has a function decode() that can be use to get a plain-text version of itself.

text = page.decode()

The above assignment sets text to be the decoded contents of the url resource named by link; that is text is a string equaling the contents of the url resource indicted by link.

The four statements form a template for getting the contents of a URL resource in string format.

import urllib.request # get module access
stream = urllib.request.urlopen( link ) # open connector to the link web resource
page = stream.read() # read contents of the resource
text = page.decode() # decode contents as normal text string

What happens next is problem-dependent.

Program `master_plan.py`

Displays the word of the day from the CS 1112 web file word-of-the-day

???

Program `secret_revealed.py`

Determines the superpower associated with a user-suppled computing id.

Some program runs

Enter computing id: mst3k

Boo-boo finding

Enter computing id: jpc

Thanato-etos cognition

Program `paging_page.py`

Displays the contents of user-indicated web page

Some program runs

Enter url: http://www.cs.virginia.edu/~cs1112/words/most-misspelled

appreciate
beautiful
cancelled
definitely
desert
diarrhea
gray
leprechaun
maintenance
neighbor
pneumonia
vacuum

Enter url: http://www.cs.virginia.edu/~cs1112/words/hangman

abated
abhors
ablush
abrade
...
zenith
zephyr
zipper
zombie

Enter url: http://www.cs.virginia.edu/~cs1112/syllabus

<!DOCTYPE html> <html lang="en"> <head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
<title>CS 1112: Spring 2020</title>
<link rel="shortcut icon" href="/~cs1112/images/favicon.ico" /><link rel="stylesheet" type="text/css" href="/~cs1112/defs/css/201-default.css"></head>
<body class="single-column-page">
<div class="task-bar">
<br/>
<table class="header-bar">
<tr style="line-height: 26px;">
<td style="text-align: center; vertical-align: middle">
<a class="menu" href="/~cs1112/term/201/">
<img style="height: 35px" src="/~cs1112/images/home.svg" alt="home icon">
</a> </td>
<td style="text-align: center; vertical-align: middle;"> <a class="menu" href="/~cs1112/software/" > <img style="height: 35px" src="/~cs1112/images/computer.svg" alt="software icon"> </a> </td>
...
<li>This syllabus is to be considered a reference document that can and will be adjusted through the course of the semester to address changing needs. It is up to the student to monitor this page for any changes. Final authority on any decision in this course rests with the professor, not with this document.</li>
</ul>
<br/>
<br/>
<br/>
<br/>
<br/>
<br/>
<br/>
<br/>
</div>
</body>
</html>

Program `get_a_dataset.py`

Gets a user-specified web csv resource as a Python dataset

Some program runs

Enter name of dataset: best-sellers.csv

['Name', 'Author', 'Language', 'Date', 'Sales']
['Don Quixote', 'de Cervantes', 'Spanish', '1605', '500000000']
['A Tale of Two Cities', 'Dickens', 'English', '1859', '200000000']
['The Lord of the Rings', 'Tolkien', 'English', '1954', '150000000']
['The Little Prince', 'de Saint-Exupery', 'French', '1943', '140000000']
["Harry Potter and the Philosopher's Stone", 'Rowling', 'English', '1997', '120000000']
['The Hobbit', 'Tolkien', 'English', '2017', '100000000']
['And Then There Were None', 'Christie', 'English', '2019', '100000000']
['Dream of the Red Chamber', 'Xueqin', 'Chinese', '1754', '100000000']
["Alice's Adventures in Wonderland", 'Carroll', 'English', '1865', '100000000']

Enter name of dataset: rows_of_stuff.csv

['Asta', 'Hachiko', 'Laika', 'Lassie']
['59.0', 'TruE']
['faLse', '3.14', '271']
['01', '10', '10.0', 'ABC']
['Asta', 'Hachiko', 'Laika', 'Lassie']
[59.0, True]
[False, 3.14, 271]
[1, 10, 10.0, 'ABC']

Resources from previous semesters are available.

Class 14 — Friday February 14

Web chrestomathics

Look both ways

Agenda

Notices

For the fun of it

To do list

Downloads

CS 1112 CSV datasets

Web programming

Program master_plan.py

Program secret_revealed.py

Some program runs

Program paging_page.py

Some program runs

Program get_a_dataset.py

Some program runs

Program `master_plan.py`

Program `secret_revealed.py`

Program `paging_page.py`

Program `get_a_dataset.py`