Class 11 – Friday, September 17

Odds, ends, and beginnings

Lest we go forward — We cannot come back again — But beware of baths

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Look both ways

• Back or ahead

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Agenda

• Extend print() function functionality

• Loop chrestomathics

• Foreshadow nested loops

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Downloads

• Program summing.py

• Accumulate a sum of values

• Program secret_decoder.py

• Chrestomathics — display a secret message using a code phrase and indices

• Program thats_printastic.py

• Introduce print() optional closing parameter end="..."

• Program c_looper.py

• Foreshadow nested looping

• Program going_rowing.py

• Introduce datasets

• Demonstrate looping through a dataset

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To do list

• Reveal one of your super power(s)

• Share a selfie

• Review class artifacts

• Complete current homework

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Numeric list paradigm — program summing.py

• Demonstrates accumulating a sum of integer values

reply = input( 'Enter a list of numbers: ' )

slist = reply.split()

nlist = []

for s in slist :

  nbr = int( s )

  nlist.append( nbr )

# by accumulation get the sum of the numbers

total = 0

for nbr in nlist :

  total = total + nbr

# print summation

print( "sum(", nlist, "):", total )

• Some program runs

Enter a list of numbers: 3 1 4 1 5 9

sum( [3, 1, 4, 1, 5, 9] ): 23

Enter a list of numbers: 58 2 37 16 99 1 9 23

sum( [58, 2, 37, 16, 99, 1, 9, 23] ): 245

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Chrestomathics — program secret_decoder.py

• Scenario

• Separately get an input code phrase and list of indices. Determine the hidden message by using the indices to peek into the code phrase. For example, suppose the code phrase equals

'abcdefghijklmnopqrstuvwxyz-'

and the indices are

[ 4, 8, 26, 4, 8, 26, 14 ]

• Then the hidden message is

'ei-ei-o'

Because s[ 4 ] equals 'e';   s[ 8 ] equals 'i';   s[ 14 ]; equals 'o';   and s[ 26 ] equals '-'.

• Algorithm

• Get the code phrase that contains hidden message.

• Clean up reply to get code phrase with no leading or trailing blank space.

• Print the code phrase.

• Get the list of indices (as string) for peeking into code phrase.

• Convert reply into a list of numeric strings.

• Build one-by-one the list of indices out of the numeric strings .

• Print the list of indices.

• Build secret message (string) by peeking into code phrase using the indices.

• Print secret message.

• Some program runs

Enter code phrase: computer

Code phrase: computer

Enter indices: 3 6 5

Indices: [3, 6, 5]

Hidden message: pet

Enter code phrase: gosh look what the cat is up to now

Code phrase: gosh look what the cat is up to now

Enter indices: 24 5 17 17 27 23 32 0

Indices: [24, 5, 17, 17, 27, 23, 32, 0]

Hidden message: sleeping

Enter code phrase: ‐abcdefghijklmnopqrstuvwxyz‐

Code phrase: ‐abcdefghijklmnopqrstuvwxyz-

Enter indices: 12 15 22 5 27 9 19 0 1 12 12 27 14 5 5 4

Indices: [12, 15, 22, 5, 27, 9, 19, 0, 1, 12, 12, 27, 14, 5, 5, 4]

Hidden message: love‐is‐all‐need

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Program thats_printastic.py

• Introduce print() optional closing parameter end="..."

• The optional end="..." parameter for a print() function allows changing from its default action of starting the next print on a new line.

• Program run

Wa-Hoo-Wa

Rah-Rah-Rah

Wa-Hoo-Wa!Rah-Rah-Rah

Wa-Hoo-Wa! Rah-Rah-Rah

s-a-i-p-p-u-a-k-i-v-i-k-a-u-p-p-i-a-s-.

s a i p p u a k i v i k a u p p i a s .

saippuakivikauppias.

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Program c_looper.py

• Foreshadow nested looping

• For a user-supplied n, prints a line of the form

row : 0 1 2 ... n-1

• Some program runs

Enter number of columns: 5

row : 0 1 2 3 4

Enter number of columns: 12

row : 0 1 2 3 4 5 6 7 8 9 10 11

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Program dataset_intro.py

• Demonstrate looping through a dataset in different ways

• Program run

table: [['A', 'B', 'C'], ['D', 'E', 'F'], ['G', 'H', 'I'], ['J', 'K', 'L', 'M']]

the table has 4 rows

row ['A', 'B', 'C'] has 3 columns

row ['D', 'E', 'F'] has 3 columns

row ['G', 'H', 'I'] has 3 columns

row ['J', 'K', 'L', 'M'] has 4 columns

row 0 : ['A', 'B', 'C']

row 1 : ['D', 'E', 'F']

row 2 : ['G', 'H', 'I']

row 3 : ['J', 'K', 'L', 'M']

 

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