Class 10 – Wednesday, September 18

Being loopy / That's so random

You did not expect – The repetition to come – You did not expect

---

Look both ways

• Back or ahead

---

Agenda

• Doing lots of loop the loops

---

Warning

• Anyone who asks me today about a function sum() earns negative ducks.

---

Hoos got your back — food insecurity

• Nationwide more than 10% of college students are not able to afford nutrious food. This problem occurs at UVA also. I am aware of two sources at UVA to help out.

• The Engineering School has a food pantry in Thornton A121. It operates on the honor system and is meant to help students with need.

• The unversity assists with the Community Food Pantry in the Runk Green Room. See the website for details.

• If you find yourself experiencing some financial hardships, please consider talking with anyone in the Undergraduate Programs Office. They can help you find even more resources.

• If you can pay it forward, please help by donating items to either pantry.

---

Downloads

• Program the_great_reverso.py

---

• Program list_creation.py

• Program list_support.py

• Program list_building.py

---

• Program numbing.py

• Program summing.py

---

• Program so_random.py

• Program and_the_winner_is.py

---

• Program bit_by_bit.py

• Program octane.py

---

• Program blast_off.py

• For the interested student — shows a counting down range.

• Recommend you try to understand it.

---

To do list

• Review class artifacts.

• Review epistles

• Complete the big_production.py as homework by Friday 4:30 PM.

---

Proof dogs are not as smart as they think they are

---

Answer accumulation

• Program the_great_reverso.py

• Produce and print the reverse of a user-supplied word (through accummulation)

Some possible program runs

Enter word: hannah

hannah

Enter word: reverse

esrever

Enter word: abcdefghijklmnopqrstuvwxyz

zyxwvutsrqponmlkjihgfedcba

---

List basics

• Program list_creation.py

s = "we are in it together"

values = [ ]

stuff = [ 'abc', 1112, 2.71, ]

digits = [ 3, 1, 4, 1, 5, 9, 2, 6 ]

words = s.split()

print( "values =", values )

print( "stuff =", stuff )

print( "digits =", digits )

print( "words =", words )

Program run

values = []

stuff = ['abc', 1112, 2.71]

digits = [3, 1, 4, 1, 5, 9, 2, 6]

words = ['we', 'are', 'in', 'it', 'together']

---

• Program list_support.py

s = "we are in it together"

values = [ ]

stuff = [ 'abc', 1112, 2.71, ]

digits = [ 3, 1, 4, 1, 5, 9, 2, 6 ]

words = s.split()

vlen = len( values )

slen = len( stuff )

dlen = len( digits )

wlen = len( words )

print( "size of", values, "=", vlen )

print( "size of", stuff, "=", slen )

print( "size of", digits, "=", dlen )

print( "size of", words, "=", wlen )

dmax = max( digits )

dmin = min( digits )

wmax = max( words )

wmin = min( words )

print( "max of", digits, "=", dmax )

print( "min of", digits, "=", dmin )

print( "max of", words, "=", wmax )

print( "min of", words, "=", wmin )

Program run

size of [] = 0

size of ['abc', 1112, 2.71] = 3

size of [3, 1, 4, 1, 5, 9, 2, 6] = 8

size of ['we', 'are', 'in', 'it', 'together'] = 5

max of [3, 1, 4, 1, 5, 9, 2, 6] = 9

min of [3, 1, 4, 1, 5, 9, 2, 6] = 1

max of ['we', 'are', 'in', 'it', 'together'] = we

min of ['we', 'are', 'in', 'it', 'together'] = are

---

• Program list_building.py

values = [ ]

values.append( "u" )

values.append( "v" )

values.append( "a" )

values.append( "!" )

values.append( " " )

values.append( "u" )

values.append( "v" )

values.append( "a" )

values.append( "!" )

print( "values =", values )

ints = []

for i in range( 0, 10 ) :

  ints.append( i )

print( "ints =", ints

Program run

values = ['u', 'v', 'a', '!', ' ', 'u', 'v', 'a', '!']

ints = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]

---

Processing a numeric list

• Program numbing.py

• Demonstrates accumulation involving a list of numbers

• Prompts and gets as input a list of integer numbers. Converts the gotten input into a list of numeric strings. Then by accumulation, converts the numeric strings one-by-one to get a list of integers (a loop is needed), where each time through the loop the current accumulation is printed.

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

slist = reply.split()

print( 'reply =', reply )

print( 'slist =', slist )

# first set up a holder of elements

nlist = [] # initialize holder to prepare for adding elements

# now get conversions of the elements of slist one-by-one

for s in slist :

  # get numeric equivalent of s

  nbr = int( s )

  # add the equivalent to the numeric list

  nlist.append( nbr )

  # print the updated list

  print( nlist )

Some possible program runs

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

reply = 3 1 4 1 5 9

slist = ['3', '1', '4', '1', '5', '9']

nlist = [3]

nlist = [3, 1]

nlist = [3, 1, 4]

nlist = [3, 1, 4, 1]

nlist = [3, 1, 4, 1, 5]

nlist = [3, 1, 4, 1, 5, 9]

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

reply = 58 2 37 16 99 1 9 23

slist = ['58', '2', '37', '16', '99', '1', '9', '23']

nlist = [58]

nlist = [58, 2]

nlist = [58, 2, 37]

nlist = [58, 2, 37, 16]

nlist = [58, 2, 37, 16, 99]

nlist = [58, 2, 37, 16, 99, 1]

nlist = [58, 2, 37, 16, 99, 1, 9]

nlist = [58, 2, 37, 16, 99, 1, 9, 23]

---

• Program summing.py

• Demonstrates accumulation involving a list of numbers

• Prompts, gets, and converts a list of integer inputs into a list of integers.

• Then by accumulation, sums the list of integers

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 possible 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

---

Introducing module random

---

• Program so_random.py

• Demonstrates some simple usage of random module function randrange()

Some possible program runs

Enter two integers: 10 100

Four random values from interval [ 0, 10 ): 7 4 3 5

Four random values from interval [ 0, 100 ): 15 28 64 87

Enter four integers: 10 20 75 100

Four random values from interval [ 0, 10 ): 4 4 8 8

Four random values from interval [ 0, 100 ): 22 64 2 80

Enter two integers: 10 100

Four random values from interval [ 0, 10 ): 1 2 8 6

Four random values from interval [ 0, 100 ): 57 63 81 18

Enter four integers: 10 20 75 100

Four random values from interval [ 10 , 20 ): 11 11 19 15

Four random values from interval [ 75 , 100 ): 89 85 76 99

Enter two integers: 2 10

Four random values from interval [ 0, 2 ): 0 1 0 1

Four random values from interval [ 0, 10 ): 6 2 7 4

Enter four integers: 0 8 31 39

Four random values from interval [ 0 , 8 ): 5 4 6 2

Four random values from interval [ 31 , 39 ): 33 33 38 34

Enter two integers: 2 10

Four random values from interval [ 0, 2 ): 1 0 0 1

Four random values from interval [ 0, 10 ): 6 6 2 8

Enter four integers: 0 8 31 39

Four random values from interval [ 0 , 8 ): 7 2 1 3

Four random values from interval [ 31 , 39 ): 37 36 32 37

---

• Program and_the_winner_is.py

• Demonstrates some simple usage of random module function randrange()

Some possible program runs

Enter a string: abcdefghij

Four random characters from string abcdefghij : e a j d

Enter some words: th fo ju ov th la lo

Four random words from list ['th', 'fo', 'ju', 'ov', 'th', 'la', 'ol'] : ov lo la ov

Enter a string: abcdefghij

Four random characters from string abcdefghij : a i b h

Enter some words: th fo ju ov th la lo

Four random words from list ['th', 'fo', 'ju', 'ov', 'th', 'la', 'ol'] : th fo th ju

Enter a string: simultaneously

Four random characters from string simultaneously : i y m t

Enter some words: 31 41 597 2 71

Four random words from list ['31', '41', '597', '2', '71'] : 71 597 31 71

---

Generating random lists of values

• Program bit_by_bit.py

• Generates a list of n bits (binary digits) for a user-supplied n.

Some possible program runs

How many bits: 8

[1, 0, 0, 0, 0, 0, 1, 1]

How many bits: 8

[1, 0, 0, 1, 1, 0, 0, 1]

How many bits: 28

[0, 1, 0, 0, 1, 1, 1, 1, 0, 0, 0, 1, 0, 0, 0, 0, 1, 0, 0, 0, 1, 1, 1, 0, 1, 1, 0, 1]

How many bits: 28

[0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 1, 1, 0, 0, 0, 0, 1, 0, 1, 0, 0, 0, 0, 1, 1]

---

• Program octane.py

• Prompts and gets three user-supplied integers s, n, and d. Uses integer s as a seed to the Python random number generator.

• Accumulates a list of n octal digits (base 8 digits; that is digits from the interval 0 to 7) one by one. Afterwards, prints the list of octal digits.

• Determines and prints the number of occurrences of d in the list of octals (check out the list module for a helpful function.

Some possible program runs

Enter three numbers: 1112 12 1

octal digit list: [4, 1, 4, 0, 6, 1, 5, 2, 5, 1, 1, 2]

number of times value 1 in list: 4

Enter three numbers: 1112 12 5

octal digit list: [4, 1, 4, 0, 6, 1, 5, 2, 5, 1, 1, 2]

number of times value 5 in list: 2

Enter three numbers: 8 9 6

octal digit list: [3, 5, 6, 2, 3, 0, 1, 2, 3]

number of times value 6 in list: 1

Enter three numbers: 8 9 6

octal digit list: [3, 5, 6, 2, 3, 0, 1, 2, 3]

number of times value 3 in list: 3

---

Decrementing range (for the interested student)

• Program blast_off.py

• Prints a user-requested count down and then prints the phrase 'Blast off!'

Some possible program runs

Enter starting and ending numbers for the countdown: 10 1

10

9

8

7

6

5

4

3

2

1

Blast off!

Enter starting and ending numbers for the countdown: 15 5

15

14

13

12

11

10

9

8

7

6

5

Blast off!

---

 

---

 

 

 
   
   
   
 

© 2019 Jim Cohoon

Resources from previous semesters are available.