Class 24 — Wednesday October 20

Module implementation and usage

Practice makes perfect — Is more than a platitude — Take it to your heart

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Look both ways

• Back or ahead

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Agenda

• Function-based chrestomathics

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Reddit video

• Check it out

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Slides

• PDF

• Show

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Downloads

• Module olio.py

• Demonstrates programmer-defined functions

• None of the functions should get input

• Tester program use_olio.py

• Performs basic testing of module olio.py

• Module primal.py

• Defines three functions relating to factorization and primality.

• None of the functions should get input or print output.

• Tester program factoid.py

• Performs basic testing of module primal.py

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To do

• Review artifacts and prior function materials.

• Complete Homework 20

• Preview next class activities activities

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Module olio

Function voting_age()

• Does not take any parameters. Returns an integer indicating how old you need to be to vote. For example, the following code segment initializes both x and y to the integer 18.

x = olio.voting_age()

y = olio.voting_age()

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Function has_blanks( s )

• Has one parameter s. Returns whether s contains at least one blank character; i.e., returns True if s contains a blank, and returns False otherwise. For example, the following code segment initializes b1 and b2 to True and False respectively.

x = 'CS 1112'

y = 'the_aardvark_said_arf_arf'

b1 = olio.has_blanks( x )

b2 = olio.has_blanks( y )

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Function great_seal()

• Does not have any parameters and does not return a value. The function prints text from the Great Seal of the United States, i.e., E Pluribus Unum.

• The code segment

olio.great_seal( )

print()

olio.great_seal( )

print()

produces as output

E Pluribus Unum

E Pluribus Unum

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Function a_ing( n )

• Has one parameter n. The function does not perform a return, instead it prints n lines of output.

• The first line prints a single 'a', the second line prints 'aa', the third line prints 'aaa', and so on. The string operator * should prove useful.

• For example usage, the code segment

olio.a_ing( 5 )

print()

olio.a_ing( 1 )

print()

olio.a_ing( 3 )

produces as output

a

aa

aaa

aaaa

aaaaa

a

a

aa

aaa

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Module primal

Purpose

• Report on factorization and primality

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Terminology

• y is a factor of x, if the remainder of x / y is 0.

• x is prime, if its only factors are 1 and itself.

• x and y are relatively prime, if y is not a factor of x and x is not a factor of y

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Observation

• The % is the Python remainder operator.

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Function is_factor( x, y )

• Parameters x and y are integers. The function returns whether y is a factor of x.

• Possible algorithm

• Determine remainder of x divided by y

• By looking at the remainder we can tell whether to return True or False

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Function is_prime( x )

• Parameter x is an integer. The function returns whether x is prime.

• Questions

• Could is_factor() help?

• What are the possible range of values do we need check for being possible factors of x.

• Does the function need a loop?

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Function are_relative_primes( x, y )

• Parameters x and y are integers. The function returns whether x and y are relatively prime.

• Questions

• Could is_prime() help?

• Could is_factor() help?

• Do we need both of them?

• Does the function need a loop?

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Slide show

 

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