---
title: Drill 11 Solution
tags: Drills-F20, 2020
---

# Drill 11 Solution

## Question 1

Fill in the function to compute the product of elements in a list of integers:

def product(lst : <blank 1>) -> <blank 2>:
  <blank 3> = <blank 4>
  for <blank 5>:
    result = result + num
  <blank 6>

::: spoiler Answer

Blank 1: `list`

Blank 2: `int`

Blank 3: `result`

Blank 4: `1`

Blank 5: `num in lst`

Blank 6: `return result`

:::

## Question 2

What does this function return when `[1, 2, 3]` is passed in?

To indicate a list, use the notation above, with brackets, commas, and each element separated by a space.

To indicate an error, type "ERROR" (without quotes).

def mystery(l : list):
    for i in l:
        return i

::: spoiler Answer

1

This function will return the first element of the list in the first iteration of the for loop.
:::

## Question 3

What does this function return when `[1, 2, 3]` is passed in?

To indicate a list, use the notation above, with brackets, commas, and each element separated by a space.

To indicate an error, type "ERROR" (without quotes).

def mystery(l : list):
    result = 0
    for i in l:
        result = i
    return result

::: spoiler Answer
3

In each iteration of the loop, `result` will be updated with the current value of `i`. In the last iteration of the loop, `result` will be updated with 3 and then returned from the function after the loop.

:::

## Question 4
What does this function return when `[]` is passed in? This is the same function as the last question.

To indicate a list, use the notation in the previous questions, with brackets, commas, and each element separated by a space.

To indicate an error, type "ERROR" (without quotes).

def mystery(l : list):
    result = 0
    for i in l:
        result = i
    return result

:::spoiler Answer

0

`result` will never be updated before it's returned from the function.
:::

## Question 5

What does this function return when [1, 2, 3] is passed in?

To indicate a list, use the notation above, with brackets, commas, and each element separated by a space.

To indicate an error, type "ERROR" (without quotes).

def mystery(l : list):
    result = 0
    for i in l:
        if i == 0:
            return False
    return True

:::spoiler Answer

True

`False` won't be returned for any of the loop values (because none of the loop values are 0). `True` will then be returned after the loop.
:::

## Question 6

True/False: If we wanted to write a function to return the third element of a list, a for-loop would be the right approach.

:::spoiler Answer
False: If we have a list li, we can access the third element with `li[2]`.
:::

## Question 7

True/False: If we wanted to write a function to count the number of times the list's third element was repeated in the list, a for-loop would be the right approach.

:::spoiler Answer
True
:::