Class 28 — Wednesday October 28

Functionization

Social distancing — Does not mean we cannot share — Love, hopes, and friendship

I have a program — That will correctly predict — Election Winner

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Look both ways

• Back or ahead

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Agenda

• Being functional

• Convert specifications dealing with strings into working functions

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Download at start of class

• Module go.py

• Tester program forth.py

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Post class

• Look over your artifacts.

• Continue to try CodingBat.

• Consider signing up for Peer Mentoring

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Homework

• Homework 25

• Implement four functions manipulating lists of strings

• Homework 26

• Predicting the 2020 US Presidential Election.

• Optional — no help from instructor or teaching assistants allowed.

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Function separate( s )

• Parameter s is a string.

• The function returns a new list where each element in the list corresponds to a character of s.

• Suppose

s1 = "apple"

s2 = "banana"

s3 = "1"

s4 = ""

• The separate() tester when given those strings as arguments to the function should produce the following output.

separate( s1 ): ['a', 'p', 'p', 'l', 'e']

separate( s2 ): ['b', 'a', 'n', 'a', 'n', 'a']

separate( s3 ): ['1']

separate( s4 ): []

• Possible algorithm

• ???

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Function ints( ns )

• Parameter ns is a string that composed of zero or more integer substrings and nothing else.

• The function returns a list of integers corresponding to the integer substrings in ns.

• FYI: The following strings do not meet the specification for the ints() parameter ns, as they all contain at least non-integer substring.

bad1 = "abc"

bad2 = "3 def 4 ghi"

bad3 = "3.14"

• FYI: The following the variable definitions all meet the specification for the ints() parameter ns, as they are composed of zero or more integer substrings and nothing else.

ns1 = " 3 "

ns2 = "12 11 -63"

ns3 = "31 415 92 653 5 9"

ns4 = " "

• The ints() tester when given those strings as arguments to the function should produce the following output.

ints( ns1 ): [3]

ints( ns2 ): [12, 11, -63]

ints( ns3 ): [31, 415, 92, 653, 5, 9]

ints( ns4 ): []

• Possible algorithm

• ???

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Function parse_phone_string( pn )

• Parameter pn is a string representing a USA phone number with an area code but without a country code. The first three digits in pn are the area code; the next three digits in pn are the prefix; and the last four digits in pn are the line number.

• The function returns a three-element integer list. The first element of the list is the pn area code in integer form; the middle element of the list is the pn prefix in integer form; the last element of the list is the pn line number in integer form

• Consider the following phone number strings

pn1 = "(201) 867-5309"

pn2 = "636-555-3226"

pn3 = "212 555 2368 (help line)"

pn4 = "888.799.9666 (customer service)"

• The parse_phone_string() tester when given those strings as arguments to the function should produce the following output.

parse_phone_string( pn1 ): [201, 867, 5309]

parse_phone_string( pn2 ): [636, 555, 3226]

parse_phone_string( pn3 ): [212, 555, 2368]

parse_phone_string( pn4 ): [888, 799, 9666]

• Possible algorithm

• ???

 

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© 2020 Jim Cohoon

Resources from previous semesters are available.