Class 08 – Friday, September 09

I know that or now I know that, that is the question

Climate change is real — Science is truth, not fake news — Help save the future

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Look both ways

• Back or ahead

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What I want to accomplish today

• Refresh what happened last class meeting

• Provide experience with string manipulation.

• Reinforce that strings are immutable — there is no Python function to change an existing string.

• Introduce looping.

• Expand problem solving skills and abilities.

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Downloads

• Program dashes.py

• Shows string operator * usage

• Program countability.py

• Introduces string method count()

• Program replacement.py

• Introduces creating new strings through replacement

• Program slice_of_pie.py

• Introduces string slicing

• Program lickety_split.py

• Lets know you know what split() really produces

• Introduces word by word looping

• Program kinda_stringy.py

• Introduces character by character looping

• Homework prowess.py

• Homework vowely.py

 

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To do list

• Check out epistle on Python list capabilities

• Check out string capabilities

• Review class artifacts

• Homework

• Check out documentation on Python random capabilities

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Program dashes.py

• Purpose

• Demonstrate string multiplication

50 * - is --------------------------------------------------

- * 50 is --------------------------------------------------

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Program escaping.py

• Program importance

• Introduces the use of Python escape character \ for representing special characters.

• Program output

a: a b c d

b: "Air quotes" are annoying

c: Hello

 

Goodbye

 

len( a ): x

len( a ): 7

len( b ): 25

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Program finding.py

• Purpose

• Introduce string method find(). The method returns where the index (location) of its substring argument.

• Program run

s: can anyone

  ----------

  0123456789 <== indices into s

t: an

s.find( t ): 1

s.find( t, 1 ): 4

s.find( t, 4 ): -1

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Program cat.py

• Purpose

• Introduce the string brackets operator [] to access individual characters in a string.

• Three program runs

Enter three indices: 0 8 9

cat

Enter three indices: 13 1 3

she

Enter three indices: 2 8 7

ram

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Program replacement.py

• Purpose

• Introduce string method replace() that returns a variant of string based on replacing its substrings.

• Two program runs

Enter text: hello mellow pillow

Enter substring (s): ll

Enter substring (r): L L

text.replace( s, r ): heL Lo meL Low piL Low # text’s s’s replaced with r’s

Enter text: jeepers creepers look at those peepers

Enter substring (s): eepers

Enter substring (r):

text.replace( s, r ): j cr look at those p # text’s s’s replaced with r’s

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Program countability.py

• Introduces string function count()

• A possible program run

Enter text: any bananas

Enter substring: an

Enter index: 7

text.count( substring ): 3 # count all

text.count( substring, 7 ): 1 # count starting from index 7

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Program slice_of_pie.py

• Purpose

• Introduce string slicing

• Three program runs

Enter favorite pie: chocolate

Enter two indices i and j: 3 8

s[ i : j ]: colat

s[ i : ]: colate

s[ : j ]: chocolat

s[ : ]: chocolate

Enter favorite pie: pizza

Enter two indices i and j: 2 3

s[ i : j ]: z

s[ i : ]: zza

s[ : j ]: piz

s[ : ]: pizza

Enter favorite pie: garlic tart

Enter two indices i and j: 1 8

s[ i : j ]: arlic t

s[ i : ]: arlic tart

s[ : j ]: garlic t

s[ : ]: garlic tart

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Program kinda_stringy.py

• Purpose

• Introduce character by character looping

• Some possible program runs

Enter text: four score

f

o

u

r

s

c

o

r

e

Enter text: step by step, inch by inch, Niagra Falls

s

t

e

p

b

y

s

t

e

p

,

i

n

c

h

b

y

i

n

c

h

N

i

a

g

r

a

F

a

l

l

s

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Problem solving — program prowess.py

• Assignment 09

• Practices some string manipulation. The program task is to

• Prompt and get a line of text.

• Determine and print the length of the text.

• Determine and print the index of last character in the text.

• Determine and print the last character of the text.

• Prints its results.

• Some possible program runs

Enter text: Hoos got your back

Input length: 18

Index of last input character: 17

Last character in text: k

Enter text: Enter text: And the winner is ...

Input length: 21

Index of last input character: 20

Last input character: .

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Problem solving — program vowely.py

• Assignment 09

• Develop a program that reports on vowel usage in some user-specified text.

• Suggestion

• When doing string analysis it is sometimes helpful to put a string in standard (canonical) form.

• Often that form is a stripped, lower case version of the string.

• Doing so here, makes the counting easier — for example, there is no need to separately count the number of a's and A's.

• Fact

• A loop is not necessary.

• Some possible program runs

Enter text: Are you doing okay today?

a: 3

e: 1

i: 1

o: 4

u: 1

Enter text: Subbookkeeper is one of my favorite words (and I am not being faceious).

a: 4

e: 7

i: 5

o: 8

u: 2

Enter text: Is rural juror a tongue twister?

a: 2

e: 2

i: 2

o: 2

u: 3

Enter text: tsk-tsk

a: 0

e: 0

i: 0

o: 0

u: 0

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