Class 24 — Wednesday October 23

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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World series

• Program astros.py

• Prints the Astros will win the world series

Astros will win the World Series

• Program nationals.py

• Prints the Nationals will win the world series

Nationals will win the World Series

• For a chance extra credit, you have until 2:15 PM to upload who will be winner of the world series.

• Cannot modify existing code of astros.py or nationals.py.

• Cannot ask me or any course personnel for insights.

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Downloads

• olio.py

• use_olio.py

• uva.py

• rotunda.py

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To do

• Look over artifacts

• Look at Hands on Python

• Look at function epistle

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Module olio.py

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_aarvark_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 uva.py

• Let's implement a worthwhile module with four functions

• A function with no parameters that does not perform an explicit return;

• A function with parameter(s) that does not perform an explicit return;

• A function with no parameters that returns something of value;

• A function with parameter(s) that returns something of value;

• Program rotunda.py

• Let's implement along the way a simple tester of module uva.py

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What's next

• Look at Hands on Python

• Two www.python.org resources should be examined now and also re-examined later.

• The Python Tutorial includes a section on functions. I recommend before going there to thoroughly review the discussion presented here.

• Python enhancement proposal 008 (PEP 008) includes recommended practices for naming modules, functions, and variables. The recommendations suggest that function and variable names are as a rule written in _snakecase; that is, lower-case words joined by underscores. Module names are expected to be short, lower-case, and no separation between words. I will add that function names are often action or verb phrases; e.g., input_integer().

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© 2019 Jim Cohoon

Resources from previous semesters are available.