Class 6 – Monday, January 28

Fearlessly we march on — strings and input

A sign for knowing — what the future asks of us — demands we act now

Wah-wah — You've given me a wah-wah — And I'm thinking of you — And all the things that we used to do — Wah-wah, wah-wah
    — George Harrison

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Look both ways

• Back or ahead

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Agenda

• Help you better model how a computer works

• Consider assignment subtleties

• Advance your chrestomathics abilities

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Illumination

• Extracts from complimenter.py submissions

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Examples

• Program math_illiteracy.py

• Demonstrates some useful math and math-like capabilities

• Two different possible runs

Python approximation of pi: 3.141592653589793

Python approximation of Euler's number: 2.718281828459045

 

sin( 30 degrees ): 0.49999999999999994

tan( 45 degrees ): 0.9999999999999999

 

Enter two numbers: 12 -15

n1 = 12

n2 = -15

 

max( n1, n2 ): 12

min( n1, n2 ): -15

 

abs( n1 ): 12

abs( n2 ): 15

Python approximation of pi: 3.141592653589793

Python approximation of Euler's number: 2.718281828459045

 

sin( 30 degrees ): 0.49999999999999994

tan( 45 degrees ): 0.9999999999999999

 

Enter two numbers: -11 19

n1 = -11

n2 = 19

 

max( n1, n2 ): 19

min( n1, n2 ): -11

 

abs( n1 ): 11

abs( n2 ): 19

• Program the_old_switcheroo.py – considers the subltety of swapping variable values

• Worksheet

• Program stringing_along.py

• Provides a deeeper introduction to the string type str

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Enquiring minds want to know

• BLS Occupational Outlook Handbook

• BLS Occupational Outlook Handbook: computing and information technology

• Job searching

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Homework requirements

• A numeric value display must be from the value of a variable; i.e., there will never be arithmetic calculations within a print() statement.

• All variables should be named indicating their purpose/usage.

• Always end each prompt with a space; e.g., input( 'What is something you consume daily?: ' )

• The testing of your programs will use inputs different from those shown in problem discussion.

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In-class homework requirements

• Demonstrate to a classmate that you have met the problem specifications. Identify those person(s) as part of the header comments for your programs.

• Ensure your checkers have also been successfully checked out by somebody(s).

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Program all_consuming.py — due Wednesday January 30

• Develop a program that estimates your annual consumption of a commodity based on how much you consume each weekday and each weekend day.

• Assumptions

• A week has 5 weekdays and 2 weekend days.

• A year has 52 weeks (yes, we know a real year is longer, but we will ignore that in this program).

• User supplied numbers are integers.

• Requirements

• The program first prompts the user for the commodity consumed.

• The program then individually prompts the user for two integer inputs: first, the quantity consumed on a typical weekday, then the quantity consumed on a typical weekend day. These are to be requested using two separate prompts.

• The program uses the inputs to compute and report the quantity consumed in a year.

• The second two prompts and the final report are to include the commodity as listed by the user in response to the first prompt. I suggest defining two prompt variables that both make use of the supplied commondity (see notes below)

• Notes

• You cannot use the comma operator (,) for concatenation (string building). If you want to build a string up, use the plus operator (+).

• After getting the commodity it might prove helpful to then set string variables (e.g., weekday_prompt and weekend_prompt or prompt1 and prompt2 or ... ) as the prompt strings for getting numeric inputs. And then use those string variables as arguments to the input() invocations.

• Suggested agorithm

• Get input commodity of interest

• Determine weekday consumption prompt

• Determine weekend day consumption prompt

• Separately get weekday and weekend day consumptions

• Compute weekly consumption

• Compute yearly consumption

• Report yearly consumption

• Two program runs

What is something you consume daily? slices of cheese

Enter slices of cheese consumed on a normal weekday: 4

Enter slices of cheese consumed on a normal weekend day: 12

You consume 2288 slices of cheese per year.

What is something you consume daily? paper napkins

Enter paper napkins consumed on a normal weekday: 6

Enter paper napkins consumed on a normal weekend day: 0

You consume 1560 paper napkins per year.

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To do list

• Homework

• Review class artifacts

• Ensure familarity by reading about Python variables, assignment, and input

• Read about Python string capabilities.

• Check out the epistles on Python and problem solving

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