Class 24 — Friday March 20

Form with function

The task before us — Turn the abstract to concrete – Functions are at hand

Being functional — Is your mantra from now on — Embrace to your core

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Look both ways

• Back or ahead

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Link to town hall meetings

• Q & A

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Agenda

• Start function-based chrestomathics

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Examples

• Module olio.py

• Program use_olio.py

• Snippet wc.py

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To do

• Look over artifacts

• Look at Hands on Python

• Look at function epistle

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Slides

• PDF

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Slides as hosted by UVA

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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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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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© 2020 Jim Cohoon

Resources from previous semesters are available.