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Lab 8 Reading, wri0ng files Modules Excep0on Handling Using lists - - PDF document

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Lab 8 Reading, wri0ng files Modules Excep0on Handling Using lists to solve problems March 13, 2018 Sprenkle - CSCI111 1 Lab 8: Pair Programming Findley Jordan Jordan Findley Parker Margaret Margaret Parker Ryan Chas Chas

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Lab 8

  • Reading, wri0ng files
  • Modules
  • Excep0on Handling
  • Using lists to solve problems

March 13, 2018 Sprenkle - CSCI111 1

Lab 8: Pair Programming

Findley Jordan Parker Margaret Ryan Chas Lizzie Robert Olivia Anna Lindsey Ben Alison Rachel Kalady Mary-Frances Joseph Andrew Harris Davis Chase Ian

March 13, 2018 Sprenkle - CSCI111 2

Jordan Findley Margaret Parker Chas Ryan Robert Lizzie Anna Olivia Ben Lindsey Rachel Alison Mary-Frances Kalady Andrew Joseph Davis Harris Ian Chase Same pairing in each table

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Pair Programming

  • Two of you

Ø double check problem requirements Ø Push each other: beWer tests, beWer comments Ø Iterate

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Compare Solu0ons

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words = sentence.split() shorthandList = [] for word in words: shorthandList.append(word[0]) shorthand = "".join(shorthandList) shorthand = shorthand.lower() print("Shorthand is:", shorthand) words = sentence.split() shorthand="" for word in words: shorthand += word[0] shorthand = shorthand.lower() print("Shorthand is:", shorthand)

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Compare Solu0ons

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words = sentence.split() shorthandList = [] for word in words: shorthandList.append(word[0]) shorthand = "".join(shorthandList) shorthand = shorthand.lower() print("Shorthand is:", shorthand) words = sentence.split() shorthand="" for word in words: shorthand += word[0] shorthand = shorthand.lower() print("Shorthand is:", shorthand)

Both are valid solutions. I’m not sure which is more efficient in practice. However, the solution at left has more conceptual complexity (appending to a list and then converting to a string, as opposed to just creating the string). In general, look for less complex solutions.

Comment Example

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def def encodeLetter(char, key): """Encodes a single character. PRE: Input parameters are a single, lowercase character string (char) and an integer key (between -25 and 25, inclusive) POST: returns the encoded character as a str"""

  • Does not say who called func0on, where parameters came

from, or where returned to

  • Any code can call the func0on and pass in input from

anywhere (e.g., hardcoded, from user input, test func0on, …)

  • Does not say variable name returned
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Review Caesar Cipher

  • Consider the following solu0ons

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for for char in in message: if if char == " ": … else else: … for for char in in message: asciiVal = ord(char) if if asciiVal == 32: … else else: …

Review Caesar Cipher

  • Consider the following solu0ons

March 13, 2018 Sprenkle - CSCI111 8

I know what " " means. I don’t immediately know what 32 means. Lesson: prefer words

  • ver numbers.

for for char in in message: if if char == " ": … else else: … for for char in in message: asciiVal = ord(char) if if asciiVal == 32: … else else: …

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Review

  • What are things we can do to lists?
  • How do we work with files?
  • What is the structure we use to do excep0on

handling?

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CREATING MODULES

March 12, 2018 Sprenkle - CSCI111 10

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Where are Func0ons Defined?

  • Func0ons can go inside of program script

Ø Defined before use/called (if no main main() func0on) Ø Or, below the main main() func0on ( )

  • Func0ons can go inside a separate module

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Crea0ng Modules

  • Modules group together related func0ons and

constants

  • Unlike func0ons, no special keyword to define a

module

Ø A module is named by its filename

  • You’ve used modules in the past

Ø graphics.py Ø game.py Just a Python file!

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Typical Use of Modules

  • Put your reusable code in a module that can be

shared with others

  • Example: game.py

Ø rollDie(sides) Ø rollMultipleDice(numDice, sides)

  • Call import game in Python interpreter

Ø What happened?

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Crea0ng Modules

  • Then, to call rollDie

rollDie func0on

Ø game.rollDie(6)

  • To access a defined constants

Ø Example: game.SIDES

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  • So that our program doesn’t execute code

automa0cally when it is imported in a program, at boWom, add

  • Note the sub-directories now listed in the

directory

if if __name__ == '__main__' : testRollDie() testRollMultipleDice()

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Crea0ng Modules

Not important how this works; just know when to use

Benefits of Defining Func0ons in Separate Module

  • Reduces code in primary driver script
  • Easier to reuse by impor0ng from a module
  • Maintains the “black box”

Ø Abstrac,on

  • Isolates tes0ng of func0on
  • Write “test driver” scripts to test func0ons

separately from use in script

March 12, 2018 Sprenkle - CSCI111 16

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Lab 8 Overview

  • Modules
  • Reading Files
  • Wri0ng Files
  • Excep0on handling
  • Func0ons/Lists

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