Class 32 — Friday November 7

Chrestomatics and patterning

The end is coming — Sooner than we want it to — Enjoy the moment

Election results — Will be coming anytime now — Which program is correct

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Look both ways

• Back or ahead

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Agenda

• Problem solving

• Image manipulation

• Admire past artistry TA favorites

• Prepare for image manipulation

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To do

• Consider practice modules

• Homework 28: image drawing (artistry.py)

• Homework 29: problem solving (tf.py)

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Downloads

• Practice module luna.py

• Practice module calc.py

• Practice module sigma.py

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Module luna.py

• Defines a function h(). The function has a single numeric parameter x. The function returns the number of hours it takes to get the moon while traveling at a speed of x miles per hour. For your information:

elapsed time = distance / speed

• For your convenience the module defines the constant

DISTANCE_IN_MILES_TO_MOON = 238900.0

• Observation: the function makes a straight-forward calculation and returns the result.

• The output of its built-in testing should be

h( 119.45 ) = 2000.0

h( 597.25 ) = 400.0

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Module calc.py

• Defines a function e(). The function has three parameters x, y, and s. Parameters x and y are decimals; parameter s is a string. If s is either '+', '-', '*', or '/', the function returns respectively x + y, x - y, x * y, or x / y. Otherwise, the functions None.

• Observation: an if-elif-...else structure is needed to determine which of five possible cases applies based on parameter s. Knowing which case applies, allows a straight-forward calculation and then the immediate return of the calculation

• The output of its built-in testing should be

19.5 + 5.25 = 24.75

12.5 - 6.5 = 6.0

12.5 * 4.5 = 56.25

10.0 / 2.25 = 4.444444444444445

1.0 @ 5.0 = None

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Module sigma.py

• Defines a function s(). The function has one parameter d. Parameter d is an already initialized integer dataset; that is, it is a list of integer lists. The function returns the sum of the dataset values. The function does not change its list parameter.

• Observation: built-in function sum() cannot handle a dataset. It can only handle a plain list.

• Observation: an accumulator is needed to store the sum of the dataset values.

• The built-in testing makes use of the following lists.

d1 = [ [ 0 ], [ 1, 2 ], [ 1, 2, 3 ], [ 0 ] ]

d2 = [ [ 1, 0, 1, 2, 2 ], [ 3, 0, 1, 1, 1, 0 ], [ 2 ], [ 0, 0, 1 ] ]

d3 = [ [ 3, 0, 3], [ 3, 0, 3, 0, 1], [ 1, 0, 2 ] ]

d4 = [ ]

• The output of its built-in testing should be

s( d1 ) = 9

s( d2 ) = 15

s( d3 ) = 16

s( d4 ) = 0

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© 2020 Jim Cohoon

Resources from previous semesters are available.