Class 07 – Wedneday, February 2

Take another step — Chrestomathics awaits you — Feel the momentum

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Look both ways

• Back or ahead

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Some directed, totally not random musings

• Complete introduction of the basics of Python programming.

• To solve fun and realistic problems we need to be able to decompose inputs into manipulable data and then be able to process the data, no matter its size. We started to wonder about this last class, when we could only capture exactly three words in three new variables.

• To process or compute regardless of size, length, or number of things requires the ability to iterate; that is, be able to repeat actions so that all the data can be processed. The slang word for iteration is looping.

• Just like how we can trace a loop of rope back to where we began, a loop in Python circles back to the lines of code where the loop began.

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Agenda

• Continue exploration of the basics of problem solving — getting data, performing computation, and displaying information

• Continue introduction to the string type str

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Downloads

• Program temperature.py

• Considers operator precedence

• Program break_the_bank.py

• Continues chrestomathics

• Program who_what_and_where.py

• Introduces type() and id() functions.

• Program the_old_switcheroo.py

• Swap the values of two variables

• Program combine_replicate.py

• Shows string + and * usage

• Program wiped.py

• Cleans up user-supplied text

• Program finding.py

• Weird world of indexing in Python

• Program thats_amore.py

• Demonstrates how to achieve capitalization possibilities

• Program finding.py

• Introduces string searching

• Program slice_of_pie.py

• Introduces string searching

• Program cat.py

• Introduces subscripting

• Program replacement.py

• Introduces creating new strings through replacement

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To do list

• Finish homework

• Check out other Python built-in functions

• Reread about Python string capabilities.

• Read Chrestomathics: part 05 if you'd like.

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Program temperature.py

• Problem

• Prompt user for a integer Celsius temperature and separately compute its integer and decimal Fahrenheit equivalent using the formula

• Two possible runs

Enter Celsius temperature: 24

24 C = 75.2 F

24 C = 75 F

Enter Celsius temperature: 8

8 C = 46.4 F

8 C = 46 F

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Program break_the_bank.py

• Homework: With a single prompt, it gets from the user four values in the following order: number of quarters, dimes, nickels, and pennies. Computes and displays how much the coinage is worth, in dollars.

• To avoid runs like the following, you are required to make use of built-in function round() to convert the calculated worth of the piggy bank to two decimal places.

• Two possible testing runs

Number of quarters, dimes, nickels, and pennies: 27 14 28 18

Coinage

    27 quarters

    14 dimes

    28 nickels

    18 pennies

are worth 9.73 dollars

Number of quarters, dimes, nickels, and pennies: 1 2 3 4

Coinage

    1 quarters

    2 dimes

    3 nickels

    4 pennies

are worth 0.64 dollars

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Program who_what_and_where.py

• Purpose

• Show memory frame information

• Introduce built-in functions id() and type().

• id( n ) identifies where in memory to find n

• type( n ) supplies what type of value is n

• Two possible program runs

Enter integer and decimal: 3 4.159

reply: 3 4.159 <class 'str'> 140400369925360

n: 3 <class 'int'> 9720640

x: 4.159 <class 'float'> 140400370194512

Enter integer and decimal: 8 8.88

reply: 8 8.88 <class 'str'> 139778356653296

n: 8 <class 'int'> 9720800

x: 8.88 <class 'float'> 139778356922448

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Program the_old_switcheroo.py

• Purpose

• Swap the values of two variables

• Worksheet: suggest you print if off and work through the code by hand

• As miswritten

reply = input( 'Enter two words: ' )

w1, w2 = reply.split()

print( )

print( 'w1 =', w1 )

print( 'w2 =', w2 )

print()

# swap the values of w1 and w2

w1 = w2

w2 = w1

# print results

print( 'After swapping' )

print()

print( 'w1 =', w1 )

print( 'w2 =', w2 )

• A program run — what is wrong?

Enter two words: wahoo wah

w1 = wahoo

w2 = wah

After swapping

w1 = wah

w2 = wah

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Program wiped.py

• Purpose

• Introduces string method strip()

• A possible program run

Enter text: scraunched is just one syllable

string of interest: scraunched is just one syllable :

  stripped version: scraunched is just one syllable :

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Program combine_replicate.py

• Introduces the string concatenation operator + and replication operator *.

• Some possible progrm runs

Enter word: fire

Enter word: fighter

Enter phrase: Wah-Hoo-Wah!

word1: fire

word2: fighter

phrase: Wah-Hoo-Wah!

### operator + performs concatenation

word1 + word2: firefighter

### operator * performs concatenation

n: 3

n * phrase: Wah-Hoo-Wah!Wah-Hoo-Wah!Wah-Hoo-Wah!

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Program thats_a_moray.py

• Purpose

• Introduce strings methods for letter casing

• Program run

s: When an Eel Climbs a Ramp to Eat Squid From a Clamp, That’s a Moray

s.lower(): when an eel climbs a ramp to eat squid from a clamp, that’s a moray

s.upper(): WHEN AN EEL CLIMBS A RAMP TO EAT SQUID FROM A CLAMP, THAT’S A MORAY

s.capitalize(): When an eel climbs a ramp to eat squid from a clamp, that’s a moray

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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 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

• 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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🦆 © 2022 Jim Cohoon

Resources from previous semesters are available.