Class 4 – Wednesday, August 31

Variation on a theme

A variable — Is like a box or a name — We must all know this

The #metoo movement — Calls out to everyone — Female Lives Matter

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Look both ways

• Back or ahead

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Aside

• Madison House plea

• Zoom information (785 886 8536) September 1st at 6 PM

• In person on September 7th in RRH 246 at 6 PM.

• Applications are due September 16th through GivePulse.

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What is happening today

• Want you to have a mental model of how to step through code.

• Become reactive

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Current and future examples (download them all, some have been updated)

• Program piaget.py

• Program intsy_bitsy.py

• Program floatilla.py

• Program variety.py

• Program psychoanalyst.py

• Program favorite_word.py

• Program hip_hopping.py

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A code walk through — getting a mental model of variables and assignment

• Slides

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Agenda

• Further expand our communication skills

• Consider abstraction

• Expand our understanding of variables

• Introduce assignment

• Introduce input acquisition

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Important questions that I hoped were answered last time

• What is a variable?

• Why is assignment so important

• Does the old value of a variable hang around for us to use?

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Whoops

• Program piaget.py

• Typos galore

• Code listing

Purpose: correct errant code

Author: Jim Cohoon

Id: jpc

  print( We learn best, when we must invent. -- Jean Piaget

• Wanted output

We learn best, when we must invent. -- Jean Piaget

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Program intsy_bitsy.py

• Problem

• Introduce the int type and integer arithmetic

• Program run

Values of interest

a: 20

b: 3

Results

a + b: 23

a - b: 17

a * b: 60

a / b: 6.666666666666667

a // b: 6

a ** b: 8000

a % b: 2

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Program floatilla.py

• Problem

• Introduce the float type and decimal arithmetic

• Program run

Values of interest

x: 2.71

y: 3.14

Results

x + y: 5.85

x - y: -0.43000000000000016

x * y: 8.5094

x / y: 0.8630573248407643

x // y: 0.0

x ** y: 22.883559193263366

x % y: 2.71

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Program variety.py

• Problem

• Perform several assignment statements including an update of a variable.

• What the solution offers

• Basic understanding of variables and assignment.

• The ability to update is crucial when problem solving.

• Check out after class

• Epistle

• Different walkthrough

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Program hip_hopping.py

• Problem

• Simulate the number of rabbits occurring over five generations.

• What the solution offers

• Examines some nuances of the assignment operator.

• Expected output

Generation: 1

Rabbits: 2

Generation: 2

Rabbits: 4

Generation: 3

Rabbits: 8

Generation: 4

Rabbits: 16

• Note for later

• The artifact version of the program updates the values of the variables in terms of themselves.

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Program psychoanalyst.py

• Problem

• Prompt and get what is on the user’s mind

• Print a reaction

• Print an out of time message.

• What the solution offers

• Introduces built-in function input(). When the function is invoked, its argument is printed to the display, the entry supplied by the user in response to that message is the value of the invocation. The input() function always returns the user reply as a string.

• The input() function allows programs to be interactive; i.e., their actions can be influenced by the user. The input() function enables Python to do general problem solving.

• Three possible program runs

Tell me what is on your mind: Worrying about the future

 

That tells me a lot about you.

 

I wish we had more time to chat. So long.

Tell me what is on your mind: Fluttering butterfly

 

That tells me a lot about you.

 

I wish we had more time to chat. So long.

Tell me what is on your mind: Is Superman colorblind

 

That tells me a lot about you.

 

I wish we had more time to chat. So long.

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Program favorite_word.py

• Problem

• Prompt and get a word of interest from user user

• Compute the length of the word

• Output a message about the length of the word

• What the solution offers

Another use of the built-in function input().

Introduces the built-in function len().

• Three possible program runs

Tell me a favorite word: crwth

 

Did you know that crwth has length 5

Tell me a favorite word: strengths

 

Did you know that strengths has length 9

Tell me a favorite word: squirreled

 

Did you know that squirreled has length 10

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Program combine_replicate.py

• Introduces the string concatenation operator + and replication operator *.

### operator + performs concatenation

a = fire

b = fighter

a + b = firefighter

### * operator produces repeated concatenation

m = Wahoo-Wah!

n = 3

m * n = Wahoo-Wah!Wahoo-Wah!Wahoo-Wah!

n * m = Wahoo-Wah!Wahoo-Wah!Wahoo-Wah!

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To do list

• Review class artifacts

• Ensure familarity with Python variables, assignment, and input

• Look over the Python string module (library)

• Read the epistle on variety.py

• Re-examine the walkthrough

• Look over another walkthrough

• Do current assignment

• Read, but do not do, the next assignment

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