9.19. Group Work: Lists

It is best to use a POGIL approach with the following. In POGIL students work in groups on activities and each member has an assigned role. For more information see https://cspogil.org/Home.

Note

If you work in a group, have only one member of the group fill in the answers on this page. You will be able to share your answers with the group at the bottom of the page.

Many interesting problems involve manipulating sequences of data. This activity should help you learn about two types of sequences in Python: lists and strings. Both lists and strings hold items in order and you can use an index to get the value at a location. The index of the first item in each is 0.

Learning Objectives

After completing this activity, Students should be able to:

• Define a list

• Identify elements of a list

• Explain the purpose of positive and negative indexes in a list

• Explain how to access individual elements of a list

• Define the following list functions: append(), insert(), remove(), len(), index(), count()

• Explain how to replace an item

Process Skill Goals

During the activity, students should make progress toward:

• Writing code that prints a list

• Writing code that edits a list - add, remove, and insert items

Edit the code below to answer the following questions.

digits = [1, 2, 0, 5, 4, 3, 6, 9, 8, 7] media = ["facebook", "twitter", "instagram", "snapchat"] studentData = [['Ethan', 13], ['Ashley', 14], ['Jalen', 12], ['Avery', 13]] print(len(digits))

Q-2: Which of the lists in the code have the most number of items?

• digits
• Correct! Digits has the most items in its lists.
• media
• Try Again! Use len() to check the length of each list
• studentData
• Try Again! Each list within a list counts as one item. Use len() to check the length of each list.
• both b and c
• Try Again! While b and c have the same number of items in their list, it is not the most. Use len() to check the length of each list

Q-3: What is printed by line 4?

Q-4: What is the index of the last item in studentData at line 3?

Construct a function that replaces a value in a list with a new specified value and returns the list with the new value.

        def replaceVal(alist, val, newval):
    idx = alist.index(val)
    alist[index] = newval
    return alist
        

Run this code to see what it prints. Feel free to edit!

areaCode = [3, 1, 2] print(areaCode * 3)

Q-7: What is printed by the following code?

• 9
• Repetition does not multiply the lengths of the lists. It repeats the items.
• [3, 1, 2, 3, 1, 2, 3, 1, 2]
• Yes, the items of the list are repeated 3 times, one after another.
• [3, 3, 3, 1, 1, 1, 2, 2, 2]
• Repetition does not repeat each item individually.
• [27, 3, 6]
• Repetition does not multiply the individual items.

Q-8: What is the index of 3 in the list areaCode?

Q-9: Which of the following lines could you use to add 7 to the list to become [3, 1, 2, 7,]?

• areaCode.append(7)
• Yes! You can add the item directly to the list using append
• areaCode.append([7])
• Try again! You cannot append a list even if it has one element
• areaCode += 7
• Try Again! You cannot concatenate a list and an integer, only two lists.
• areaCode.extend([7])
• Yes! You can add a list to the end of another list using extend.
• areaCode.extend(7)
• Try again! You cannot extend a list with a number.

Construct a function that returns the max value from a list. If there are no items in alist``return ``None.

        def getMax(alist):
---
    if len(alist) == 0:
        return None
---
    curr = alist[0]
    for item in alist:
---
        if item > curr:
---
            curr = item
---
    return curr
        

Run this code to see what it prints. Feel free to edit!

bigCities = ["Chicago", "Detroit", "Houston", "New York"] print(bigCities) for x in bigCities: print(x, end = " ") print()

Q-12: How many items are in the list bigCities?

Q-13: What is the index of “Detroit” in the list bigCities?

• 2
• Try Again! Remember that the index starts at 0 not at 1.
• 1
• Yes, because lists start 0 based index, the solution would be index 1.
• 0
• Try Again! Use index("Detroit") to find the index.
• 3
• Try Again! Use index("Detroit") to find the index.

Construct a function that returns the average of the values entered into the list.

        def average():
---
    numlist = list()
    while (True):
---
        inp = input('Enter a number: ')
---
        if inp == 'done': break
---
        value = float(inp)
---
        numlist.append(value)
---
    average = sum(numlist) / len(numlist)
---
    print('Average:', average)
        

Q-15: Drag each term to its definition Read the chapter on lists and try again.
• count
• Returns the number of times a specified value appears in the list
• append
• Adds a value to the end of a list.
• len
• Returns the number of items in a list.
• remove
• Removes an item from a list.
• type
• Returns the class name (type) of the current object.

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