Day 2 — Optional Exercises

Control flow, loops, lists, tuples, sets

These exercises practice Day 2 material: branching with elif/else, for and while loops, lists, tuples, sets. Plan on 45–60 minutes.

Solutions are in Day_2_Solutions.qmd. Try first; check after.

Exercise 1 — Nested conditionals

A polling place needs to determine what to do with a person who walks in. Write a script using nested if/elif/else that:

  • Takes is_registered (True/False) and at_correct_precinct (True/False) as variables.
  • Prints "Allow to vote" if both are True.
  • Prints "Redirect to correct precinct" if registered but at the wrong precinct.
  • Prints "Provisional ballot" if not registered.

Test all three scenarios.

# your code here

Exercise 2 — for loop with a list

Given a list of US presidents:

presidents = ["Washington", "Adams", "Jefferson", "Madison", "Monroe"]
  1. Write a for loop that prints each president’s name preceded by "President ".
  2. Write a second for loop that uses a counter variable to print each president with their number, like "#1: Washington".
# your code here

Exercise 3 — while loop with a condition

Write a while loop that finds the smallest number greater than 100 that is divisible by both 7 and 11.

(Hint: use the modulo operator % and start at 101.)

# your code here

Exercise 4 — Nested while loops

Presidential elections happen every four years, in years divisible by 4 (2020, 2024, 2028, …). Write a nested while loop that, for each year from 2020 through 2030:

  • Counts how many years it takes to reach the next presidential election year.
  • Prints a sentence like "2021 reaches a presidential election year (2024) in 3 years."

Years that are already election years should report 0 years.

(Hint: the outer loop iterates years 2020–2030. The inner loop counts steps until the year is divisible by 4. Look back at the multiples-of-13 example in the slides if you’re stuck.)

# your code here

Exercise 5 — List operations

Given:

states = ["Ohio", "Florida", "Pennsylvania", "Wisconsin", "Michigan"]
  1. Add "Arizona" to the end of the list (use a list method, not reassignment).
  2. Insert "Georgia" at position 2.
  3. Remove "Florida" from the list.
  4. Sort the list alphabetically.
  5. Print the final list and its length.
# your code here

Exercise 6 — Iterating over two lists

You have a list of senators and their years of service:

senators = ["Sanders", "Warren", "Cruz", "Cornyn", "Schumer"]
years = [34, 12, 13, 23, 26]

Write a for loop that iterates over both lists by index, and prints each senator’s name with their years served — but only if they’ve served more than 15 years.

(Hint: use range(len(senators)) to get an index, then access each list with [i].)

# your code here

Exercise 7 — Sets

You have two lists of co-sponsors on two pieces of legislation:

bill_a_sponsors = ["Sanders", "Warren", "Klobuchar", "Booker", "Brown"]
bill_b_sponsors = ["Warren", "Booker", "Markey", "Whitehouse", "Klobuchar"]

Using sets:

  1. Find the senators who co-sponsored both bills.
  2. Find the senators who co-sponsored bill A but not bill B.
  3. Find the total number of unique senators across both bills.
# your code here

Exercise 8 — Putting it together

A short data-cleaning task. You have a list of vote counts that includes some -1 values (meaning “missing data”):

vote_counts = [4250, 3980, -1, 5120, 2890, -1, 6400, 4100]

Write a script that:

  1. Uses a for loop to compute the mean of only the valid (non-missing) vote counts.
  2. Counts how many missing values there were.
  3. Prints both numbers in a single f-string sentence, e.g., "Mean: 4456.7 (3 missing values dropped)".
# your code here