Class 22 — Wednesday March 14

Test examples and "while" examples

This is the beginning of anyting you want

Look both ways

Back or ahead

Agenda

Continue exploration while statement and of if statement

Test practice

To do

Examine artifacts on collab.

Examine while epistle

Prepare for after the test by looking at dict module documentation

Homework

More 'while' Examples and Test Review

Program keep_quizzing.py

Program first_five_proper.py

Program guess_computer_number.py

Program binary_checkerboard.py

Program leap_year.py

Problem keep_quizzing.py

Program an automated grading system that allows the student user to keep taking quizzes until they reach a desired average.

First, the user is prompted to enter their desired score, out of 100.

Next, the user enters their first quiz score, out of 100.

While their running average quiz score is less than their desired grade, the user will be prompted to enter more quiz scores.

Once their running average is greater than or equal to their desired score, the program congratulates the user, and prints out their final total.

Some program runs

Enter desired score: 92

Enter quiz score: 87

Enter quiz score: 88

Enter quiz score: 97

Enter quiz score: 99

Congratulations! Your average score is 92.75

Enter desired score: 88

Enter quiz score: 90

Congratulations! Your average score is 90.0

Problem first_five_proper.py

The computer takes names from the user one at a time.

Once the user has typed 5 properly capitalized names (first letter capitalized, rest of name lower case), the computer prints out a list of just those 5 names. Note that the user need not type 5 "correct" names in a row.

Enter name: Elizabeth

Enter name: Rachel

Enter name: Luther

Enter name: ray

Enter name: Nate

Enter name: Upsorn

[Elizabeth, Rachel, Luther, Nate, Upsorn]

Enter name: Aphrodite

Enter name: Hera

Enter name: Demeter

Enter name: Diana

Enter name: Cupid

[Aphrodite, Hera, Demeter, Diana, Cupid]

Test prep: leap_year.py

The computer takes in a year from the user.

If the year is divisible by 4, the programs prints out "It's a leap year"

If the year is divisible by 2, but NOT divisible by 4, the programs prints out "It's a Winter Olympics year."

If the year is not divisible by 2, the programs prints out "It's a regular year."

Test prep: binary_checkerboard.py

This program prints out a table (like digitbox) that is a checkboard pattern.

The 0th row and 0th column entry is 0. From there, alternate 1's and 0's.

Hint: Use the sum of the row and column index to determine whether to enter a 1 or 0 for a specific cell.

Test prep: guess_computer_number.py

The program generates a random number and prompts the user to guess. After every guess, the program replies "higher", "lower", or "equal to".

Agenda

Introduce dict

To do

Examine artifacts

Examine dict module documentation

Examine collections epistle

Examine while epistle

Homework

Examples

Program romantic.py

Program unromantic.py

Program floradation.py

Program even_odd.py

Program good_doggie.py

Some data sets

romans.csv

babelfish

Problem romantic.py

Get a roman numeral and determine its integer equivalent

Some program runs

Enter Roman numeral: V
5

Enter Roman numeral: d
500

Enter Roman numeral: 0
Unknown

Problem unromantic.py

Get a word and print its English equivalent

Some program runs

RecursionError: maximum recursion depth exceeded during compilation

Discussion

Repeat the word carrot ten times out loud

The human brain is great with associations; e.g., many of us associate apple with red, sky with blue, and programming with fun.

A dict is Python's software equivalent of a collection of associations. In particular, a dict is an un-ordered collection of associations.

The elements of a dict are called mappings. A mapping associates one object (called the key) with another object (called the value).

The literal for an empty dict is {}.

A literal mapping is written using the : to separate the key with its value. For example, the below variable flora_to_color is a dict that associates flora with colors.

flora_to_color = { 'spruce': 'green', 'apple': 'red', 'shamrock': 'green',
'banana': 'yellow', 'potato': 'brown', 'eggplant': 'purple' }

The len() function works on a dict. For example, len( flora_to_color ) is 6, because the definition of flora_to_color specified six mappings.

The brackets [] operator in conjunction with assignment can be used to put a mapping into a dict. For example, the statement below adds the mapping 'lemon' to 'yellow'.

flora_to_color[ 'lemon' ] = 'yellow'

The keys of a dict are always distinct. So, the following statement

flora_to_color[ 'potato' ] = 'golden'

would cause flora_to_color to lose its association of mapping potato to brown — its association with 'potato' is now only to golden.

As our flora_to_color example shows, the values of a dict are not necessarily unique.

Python dict's have functions keys() and values() for getting a hold of keys and values.

the_keys = flora_to_color.keys()
the_values = flora_to_color.values()

While there are never any duplicates in the keys, depending upon the dictionary there may be duplicates in the values.

Other information about dict objects are listed below. In the below, assume that d is a dict.

d.get(k) returns the value that key k maps to in d. If there is no such value, returns None.

d[k] returns the value that key k maps to in d. If there is no such value, an exception (error) occurs.

(k in d) indicates whether k is a key value in d.

(k not in d) indicates whether k is not a key value in d.

d.clear() removes all mappings in d.

del d[k] removes k’s mapping in d.

Information on a dict is available in the module documentation section of the website.

Additional information on collections is in general is available in the collections epistile.

Problem even_odd.py

Introduce the Python dict data structure

Some program runs

Enter a number: 3
3 odd

Enter even or odd: even
a number is even if its remainder divided by 2 is 0

Enter a number: 6
6 even

Enter even or odd: odd
a number is odd if its remainder divided by 2 is 1

Problem good_doggie.py

For a series of dog information requests, the program reports what it knows about the dog.

Its dog information data source is located at URL

http://www.cs.virginia.edu/~cs1112/datasets/csv/puppies.csv

Brainstorming

How should we store the dog information?

How do we get and store the input?

How many times do we set up the dog information

What times of loops do we need?

Sequential

Nested

Mixture of nested and sequential

Where am I

Resources from previous semesters are available.