Class 06 – Monday, September 5

Fearlessly we march on — variables and strings

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

I say love is love — For aren’t we all just people — Living as we are

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Look both ways

• Back or ahead

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Agenda

• Reconsider last class

• Advance your chrestomathics abilities

• Round a decimal using built-in function round()

• String method split()

• Chrestomathics

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Examples

• Program iiiii.py

• Another try at repeated variable incrementing

• Program being_powerful.py

• Gets decimal input

• Program trio.py

• Introduces string method function split()

• Program i_get_around.py

• Shows use of function round()

• Program escaping.py

• Explores the use of Python escape character \ for representing special characters.

• Program all_consuming.py

• Chrestomathics

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Program iiiii.py

• Another try at repeated variable incrementing by really look at what is going on in the following code.

# define an iterator variable named i, and initialize it to 0

i = 0

   

print( "i:", i )

print()

   

# increment i by one (for the first time)

i = i + 1 # i's new value is its current value plus 1

   

print( "i:", i )

print()

   

# increment i by one (for a second time)

i = i + 1 # i's new value is its current value plus 1

   

print( "i:", i )

print()

   

# increment i by one (for a third time)

i = i + 1 # i's new value is its current value plus 1

   

print( "i:", i )

print()

   

# increment i by one (for a fourth time)

i = i + 1 # i's new value is its current value plus 1

   

print( "i:", i )

print()

   

# increment i by one (for a fifth time)

i = i + 1 # i's new value is its current value plus 1

   

print( "i:", i )

print()

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Program being_powerful.py

• Problem

• Prompt and get an integer number (the base for the computation)

• Prompt and get a decimal number (the exponent for the computation)

• Compute the value of the integer to power of the decimal number

• Print the result of the computation

• What the solution offers

• Uses the built-in cast functions int() and float() to convert numeric strings into the numbers they represent.

• Why else is it important

• The program has four parts that can serve as a template for much of our future problem solving.

• Get inputs

• Massage inputs into needed values

• Compute result

• Print result

• Three possible program runs

Enter base (integer): 2

Enter exponent (decimal): 0.5

1.4142235623730951

Enter base (integer): 11

Enter exponent (decimal): 3.14

1861.971509290233

Enter base (integer): 4

Enter exponent (decimal): 0.333

1.5866676863822857

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Program trio.py

• Problem

• From a single input request determine the three words the user supplies

• Why is it important

• Introduces string method function split()

• Two possible program runs

Enter three words: peace joy friends

Your words

peace

joy

friends

Enter three words: ready or not

Your words

ready

or

not

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Program i_get_around.py

• What it offers

• Introduces function round()

• Two possible program runs

Enter number: 3.1415926

number: 3.1415926

round( number ): 3

round( number, 6 ): 3.141593

round( number, 5 ): 3.14159

round( number, 4 ): 3.1416

round( number, 3 ): 3.142

round( number, 2 ): 3.14

round( number, 1 ): 3.1

round( number, 0 ): 3.0

Enter number: 2.7182818

number: 2.7182818

round( number ): 3

round( number, 6 ): 2.718282

round( number, 5 ): 2.71828

round( number, 4 ): 2.7183

round( number, 3 ): 2.718

round( number, 2 ): 2.72

round( number, 1 ): 2.7

round( number, 0 ): 3.0

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Program escaping.py

• Program importance

• Introduces the use of Python escape character \ for representing special characters.

• Program output

a: a b c d

b: "Air quotes" are annoying

c: Hello

 

Goodbye

 

len( a ): x

len( a ): 7

len( b ): 25

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Program all_consuming.py

• Develop a program that estimates the annual consumption of a commodity based on how much is consumed on both a typical weekday and on a typical weekend day.

• Due time: Thursday, September 8

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Assumptions

• The term week denotes 5 weekdays and 2 weekend days.

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

• User supplied inputs are integers.

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Requirements

• The program prompts the user for the commodity to analyze.

• The program then individually (i.e., separarely) prompts the user for two integer values:

• First, the quantity consumed on a typical weekday,

• Then the quantity consumed on a typical weekend day.

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

• The quantity output should specify the commodity whose use is being reported.

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Suggested agorithm

• Get input commodity of interest

• Get weekday consumption

• Get weekend day consumption

• Compute weekly consumption

• Compute yearly consumption

• Report yearly consumption

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Three program runs

What is something you consume daily? paper napkins

How much consumed on a typical weekday: 6

How much consumed on a typical weekend day: 0

You consume 1560 paper napkins per year.

What is something you consume daily? pretzels

How much consumed on a typical weekday: 0

How much consumed on a typical weekend day: 1

You consume 104 pretzels per year.

What is something you consume daily? jelly beans

How much consumed on a typical weekday: 4

How much consumed on a typical weekend day: 12

You consume 2288 jelly beans per year.

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To do list

• Homework

• Review class artifacts

• Read about strings: sections 04 and 05

• Read more about strings

• Check out the epistles on Python and problem solving

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All you need is love — All you need is love — All you need is love, love — Love is all you need.     The Beatles

 

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