Sequences of Data & Scope

CS 110

Reminders and Announcements

• Ex 3 due Tonight!
• Couple of new functions (wedge and portion) if you’re interested - see edSTEM!
• Quiz 1 coming up next week (no Tutorial next week; Ex 4 will be focused on reading programs rather than writing them)
• Students with testing accommodations have already received an email from me
• Deadline to let me know of any grading issues (tutorials, MQs, etc. is the start of Q1). After that point, all grades are locked in.

Next Week

• Monday - Q1 Review (In-Person MQ 7)
• Wednesday - Quiz 1 in-class
• Friday - Intro to Control Flow
• Ex 4 Due

Quiz 1 - Wednesday (2/5)

• In-person here in our normal classroom during our normal time.
• Taken on the Lockdown Browser on your personal computer; details on how to set it up are on our Canvas page as well as on the Quiz 1 page.
• Make sure to try the Lockdown Browser version of the Practice Quiz before Monday.
• You must be able to connect to eduroam
• You must bring your Wildcard
• YOU WILL NOT RECEIVE EXTRA TIME IF YOU COME TO THE QUIZ WITHOUT IT SETUP.
• Problems are closer to our mini-quiz and the canvas practice quizzes
• Covers everything up to and including Monday
• Specifically won't emphasize memorization though the functions highlighted on the study guide you should know how to call without any other help
• CHARGE YOUR COMPUTER THE NIGHT BEFORE.

Academic Integrity

• You are encouraged to ask one another questions about assignments, but you must do your own work.
• Easy way to avoid: do not look at anyone's code other than mine or your own. This includes people who are not in our class.
• We will consider the following to be academic violations:
• Turning in someone else’s file or asking someone else to write it for you.
• Reading and reproducing someone else’s code for a problem
• Cutting, pasting, transcribing, etc. someone else’s code, in whole or in part
• Allowing anyone else to type or edit your code other than someone on the course staff.
• Giving your code to someone else or posting your code in any public location
• Using any tools to generate code for ANY assignment in this course.
• Everything you submit in this class is subject to an in-person audit by course staff.
• If at any point you write a program you can’t explain, you should stop.

Sequences: Why are they useful?

• Allows us to store collections of data and allow us to easily read and process data via loops

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• Examples:
• A sequence of notes for creating songs
• A sequence of colors to make a color palette
• A pair of coordinates (x,y)
• A sequence of coordinates to draw shapes (points, lines, polygons)
• A sequence of canvas objects that you can move and interact with
• ...

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New Data Type: Tuple

• A tuple is an immutable sequence of values.
• Useful for organizing and conveniently accessing related data.
• In Python we define them like this:

tuple_of_strings = ("first year", "sophomore", "junior", "senior")�

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Tuples: The Rules

• The items in a tuple can be of any type
• A tuple can be of any length
• You can access any tuple element through 0-based indexing
• You can slice tuples
• You cannot edit tuples (immutability)
• You can concatenate tuples to create new, longer tuples

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New Data Types: Lists and Tuples

A list is a mutable sequence of values:�

empty_list = []

list_of_strings = ["first year", "sophomore", "junior", "senior"]

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A tuple is an immutable sequence of values:�

empty_list = ()

tuple_of_strings = ("first year", "sophomore", "junior", "senior")

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Lists: The Rules

• The items in a list can be of any type
• A list can be of any length
• You can access any list element through 0-based indexing
• You can slice a list
• You can edit a list (mutable)
• You can concatenate lists using the + operator
• You can sort lists (as long as Python knows how to sort your data)
• You can add elements to a list using the append function
• You can remove elements in a list using the pop function
• You can update specific elements in a list using the offset notation from #3.

my_list = [8, 3, 2, 5, 7]

# Access items by index

my_list[len(my_list) - 1]

my_list[4]

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The Substitution Model

nums = [3.3, 4, 6, 3, 1.2, 1.4]

result = nums[0] + nums[2] + nums[4]

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The Substitution Model

nums = [3.3, 4, 6, 3, 1.2, 1.4]

result = nums[0] + nums[2] + nums[4]

3.3 + 6 + 1.2

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The Substitution Model

nums = [3.3, 4, 6, 3, 1.2, 1.4]

result = nums[0] + nums[2] + nums[4]

3.3 + 6 + 1.2

print(result)

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The Substitution Model

nums = [3.3, 4, 6, 3, 1.2, 1.4]

result = nums[0] + nums[2] + nums[4]

3.3 + 6 + 1.2

print(result)

10.5

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Substitution Model

print(randint(0,10) + 6 * 3)

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Substitution Model

print(randint(0,10) + 6 * 3)

print( 3 + 6 * 3)

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Substitution Model

print(randint(0,10) + 6 * 3)

print(21)

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Substitution Model

my_list = [(0, 1), (1, 8), (3, 9), (4, -5)]

print(my_list[0])

Substitution Model

my_list = [(0, 1), (1, 8), (3, 9), (4, -5)]

print(my_list[0])

print( (0, 1) )

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Substitution Model

my_list = [(0, 1), (1, 8), (3, 9), (4, -5)]

print(my_list[0])

print( (0, 1) )

(0, 1)

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Substitution Model

my_list = [(0, 1), (1, 8), (3, 9), (4, -5)]

print(my_list[2][1])

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Substitution Model

my_list = [(0, 1), (1, 8), (3, 9), (4, -5)]

print(my_list[2][1])

print( (3,9)[1])

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Substitution Model

my_list = [(0, 1), (1, 8), (3, 9), (4, -5)]

print(my_list[2][1])

print( 9)

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Substitution Model

my_list = [(0, 1), (1, 8), (3, 9), (4, -5)]

print(my_list[2][1])

print( 9)

9

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Variable Scope

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Scope

• Scope — refers to the part of the program where a variable is accessible
• Global variable — a variable which is defined in the main body of a file (best avoided)
• Local variable — a variable which is defined inside a function. Not accessible from outside the function
• The parameter names in the function definition behave like local variables, but they contain the values that we pass into the function when we call it.

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Source: https://python-textbok.readthedocs.io/en/1.0/Variables_and_Scope.html

Scope 1: Consider the following program...

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def demo_1(name):

greeting = 'Welcome, ' + name

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demo_1('Jimmy')

print(greeting)

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Scope 1: Local variables cannot be accessed outside function

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def demo_1(name):

greeting = 'Welcome, ' + name

demo_1('Jimmy')

print(greeting)

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�TAKEAWAY: If you want access to a value after the function ends, you have to return it. WE CAN TURN THIS INTO A GOOD PROGRAMMING PRACTICE.

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name = 'Lindsay'

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def demo_2(name):

print(name)

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demo_2('Walter')

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TAKEAWAY: Local variables take precedence over global variables. THIS IS A BAD PROGRAMMING PRACTICE

Scope 2: Which name will print to the screen?

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Scope 3: Global variables can be accessed inside a function

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name1 = 'Lindsay'

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def demo_3(name):

print(name)

print(name1)

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demo_3('Walter')

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THIS IS AN OKAY (BUT NOT GREAT) PROGRAMMING PRACTICE

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Scope 4: Python assumes you’re creating a new local variable

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�name = 'Lindsay'

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def modify_name(new_name):

name = new_name

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print(name)�modify_name('Walter')�print(name)

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WOOF. Don't do this.

Note: We won’t do this until after Q1. I’m just putting this here for those who want to know if you CAN do this.

Scope 5: Global variables can updated with global keyword

name = 'Lindsay'

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def modify_name(new_name):

global name

name = new_name

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print(name)�modify_name('Walter')�print(name)

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