Popcorn Hack 1

Code Runner Challenge

Lists Popcorn 1 - predict, run, fix the crash

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# CODE_RUNNER: Lists Popcorn 1 - predict, run, fix the crash
#Convert the above CollegeBoard Psuedocode into Python code and run it.
#Predict the output of each print statement before running the code. Add your prediction as a comment next to each print statement.

items_needed = ["blankets", "socks", "water", "meals"] # 4 items, so valid Python indexes are 0 through 3

print(items_needed[0])                     # Prediction: blankets (first item, index 0 in Python vs 1 in pseudocode)
print(items_needed[len(items_needed) - 1]) # Prediction: meals (last item; Python's last index is len - 1, pseudocode's is LENGTH)
print(len(items_needed))                   # Prediction: 4
print(items_needed[3])                     # Prediction: IndexError with items_needed[5]. FIX: changed to [3], the last valid index -> meals

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Output

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Popcorn Hack 2

Code Runner Challenge

Lists Popcorn 2

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# CODE_RUNNER: Lists Popcorn 2
#Now try it yourself! Write a for loop that calculates the sum of all the volunteer hours in the list and prints it out.
#Calculate the average of the volunteer hours in the list using the value you calculated for the sum and the length of the list and print it out.

volunteer_hours = [7, 6, 8, 5, 7, 9]

total = 0                          # Initialize the accumulator BEFORE the loop
for hours in volunteer_hours:
    total += hours                 # Add each element inside the loop

print(f"Total: {total}")           # 42

# FIX: guard against an empty list so we never divide by zero (ZeroDivisionError)
if len(volunteer_hours) == 0:
    print("No data yet")
else:
    average = total / len(volunteer_hours)
    print(f"Average: {average}")   # 7.0

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Output

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Popcorn Hack 3

Code Runner Challenge

Lists Popcorn 3 - count then filter

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# CODE_RUNNER: Lists Popcorn 3 - count then filter
items_requested = ["blankets", "socks", "meals", "socks", "water", "socks", "meals"]   # use real class data

frequency = {}
for item in items_requested:
    if item in frequency:
        frequency[item] += 1
    else:
        frequency[item] = 1

print(frequency)

# 1. Build a list of items with 2 or more votes
popular = []
for item in frequency:
    if frequency[item] >= 2:
        popular.append(item)

# 2. Print that list
print(popular)

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Output

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Homework

Code Runner Challenge

Lists Homework - indexing, accumulator, count and filter on one dataset

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# CODE_RUNNER: Lists Homework - indexing, accumulator, count and filter on one dataset
donations_by_item = ["blankets", "socks", "blankets", "water", "socks", "blankets",
                      "meals", "socks", "blankets", "water", "blankets", "socks"]

costs = [2, 3, 2, 4, 3, 2, 1, 3, 2, 4, 2, 3]

# LESSON 1 - indexing
# 1. Print how many donations were made
print(len(donations_by_item))

# 2. Print the last donation using indexing
print(donations_by_item[-1])

# LESSON 2 - sum and average
# 3. Use a loop to total costs (do NOT use sum())
total = 0
for cost in costs:
    total += cost

# 4. Print "Total: <total>" and "Average: <average>" as integers using the int() function
average = total / len(costs)
print(f"Total: {int(total)}")
print(f"Average: {int(average)}")

# LESSON 3 - count and filter
# 5. Build a frequency dictionary of donations_by_item and print it
frequency = {}
for item in donations_by_item:
    if item in frequency:
        frequency[item] += 1
    else:
        frequency[item] = 1
print(frequency)

# 6. Build a list of items with 3 or more donations and print it
popular_items = []
for item in frequency:
    if frequency[item] >= 3:
        popular_items.append(item)
print(popular_items)

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Output

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