The Perfect Crab — Exercise Solutions

🌱

Foundations

Functions, arithmetic, expressions, state & variables

12 files

#010 — Comments

Info

#011 — Identity

Demo

Output

just_return_it(4) returns:
4

#012 — Add One

Demo

Output

add_one(6) returns:
7

#013 — Add Two

1 check passed

Solution

def add_two(num):
  return num + 2

Output

Function: add_two
EXPECTED: 8
ACTUAL:   8
That's correct! (1 checks right so far)

#014 — Multiply Numbers

Demo

Solution

def multiply_numbers(num_a, num_b):
  return num_a * num_b # That `*` means multiply

Output

multiply_numbers(2, 3) is:
6
multiply_numbers(3, 5) is:
15

#015 — Add Numbers

2 checks passed

Solution

def add_numbers(num_a, num_b):
  return num_a + num_b

Output

add_numbers(2, 3) is:
EXPECTED: 5
ACTUAL:   5
That's correct! (1 checks right so far)

add_numbers(3, 5) is:
EXPECTED: 8
ACTUAL:   8
That's correct! (2 checks right so far)

#016 — Operators

Demo

Output

2 + 3 = 5 (should be 5)
2 * 3 = 6 (should be 6)
2 - 3 = -1 (should be -1)
2 / 3 = 0.6666666666666666 (should be 0.6666666666666666)
3 % 2 = 1 (should be 1)
2 // 3 = 0 (should be 0)
2 ** 3 = 8 (should be 8)

#017 — Expressions

Info

#018 — Statements

Demo

Output

My favourite number is: 99
---
Today's day is: 20
---

#019 — State

Demo

Output

a is 20
b is 20

#020 — State Tables

Demo

Output

a is 20
b is 20

#021 — Two Step

3 checks passed

Solution

def add_one_and_divide_by_two_with_statements(num):
  added = num + 1
  halved = added / 2
  return halved

def add_one_and_divide_by_two_with_an_expression(num):
  return (num + 1) / 2

def divide_by_two_and_add_one(num):
  # Divide num by two and add one to the result
  return num / 2 + 1

def multiply_by_forty_and_add_sixty(num):
  # Multiply num by forty, and then add sixty
  return num * 40 + 60

def add_together_and_double(num_a, num_b):
  # Add together num_a and num_b, then double the result
  return (num_a + num_b) * 2

Output

add_one_and_divide_by_two_with_statements(5) is:
3.0
add_one_and_divide_by_two_with_an_expression(5) is:
3.0

Function: divide_by_two_and_add_one
EXPECTED: 4.0
ACTUAL:   4.0
That's correct! (1 checks right so far)


Function: multiply_by_forty_and_add_sixty
  ...

📝

Strings

Creation, indexing, operations & concatenation

4 files

#022 — Strings

Demo

Output

Kay
Claude

#023 — String Indexing

8 checks passed

Solution

def get_first_letter(the_str):
  # Return the first letter of the string
  return the_str[0]

def get_last_letter(the_str):
  # Return the last letter of the string
  return the_str[-1]

def get_nth_letter(the_str, n):
  # Return the letter of the string at the specified index
  return the_str[n]

def get_letters_between_four_and_eight(the_str):
  # Return the section of the string between indexes four and eight
  return the_str[4:8]

Output

The Most Perfect Crab
T
b
s
The

Function: get_first_letter
EXPECTED: T
ACTUAL:   T
That's correct! (1 checks right so far)

EXPECTED: F
  ...

#024 — String Operations

6 checks passed

Solution

def make_uppercase(string):
  # Return the string in uppercase
  return string.upper()

def make_lowercase(string):
  # Return the string in lowercase
  return string.lower()

def strip_whitespace(string):
  # Return the string with any whitespace removed from the start and end
  return string.strip()

Output

The string is 6 characters long

Function: uppercase
EXPECTED: HELLO
ACTUAL:   HELLO
That's correct! (1 checks right so far)

EXPECTED: WORLD
ACTUAL:   WORLD
That's correct! (2 checks right so far)


  ...

#025 — String Concatenation

2 checks passed

Solution

def greet(name):
  # Return the string "Hello, Kay!" where "Kay" is the name provided
  return f"Hello, {name}!"

Output

Anteater
Forty2
Hello, Kay!
Your name is 3 characters long

Function: greet
EXPECTED: Hello, Chuang-tzu!
ACTUAL:   Hello, Chuang-tzu!
That's correct! (1 checks right so far)

EXPECTED: Hello, Crab!
ACTUAL:   Hello, Crab!
  ...

🔀

Conditionals

If/else, comparison & logical operators

3 files

#026 — Ifs

6 checks passed

Solution

def is_first_of_the_month(day_number):
  # Return "First of the month!" if the day number is 1.
  # Return "Not first of the month" otherwise.
  if day_number == 1:
    return "First of the month!"
  else:
    return "Not first of the month"

def has_five_chars(the_str):
  # Return "STRING is five characters long" if the string is five characters
  # long.
  # Otherwise, return "Not five characters".
  if len(the_str) == 5:
    return f"{the_str} is five characters long"
  else:
    return "Not five characters"

Output

It must be winter — or a dead tree
It must be winter — or a dead tree

Function: is_first_of_the_month
EXPECTED: First of the month!
ACTUAL:   First of the month!
That's correct! (1 checks right so far)

EXPECTED: Not first of the month
ACTUAL:   Not first of the month
That's correct! (2 checks right so far)

  ...

#027 — Comparison

20 checks passed

Solution

def a_is_equal_to_b(a, b):
  return a == b

def a_is_less_than_b(a, b):
  return a < b

def a_is_greater_than_b(a, b):
  return a > b

def a_is_less_than_or_equal_to_b(a, b):
  return a <= b

def a_is_greater_than_or_equal_to_b(a, b):
  return a >= b

def a_is_not_equal_to_b(a, b):
  return a != b

def a_is_within_b(a, b):
  return a in b

Output

Function: a_is_equal_to_b
EXPECTED: True
ACTUAL:   True
That's correct! (1 checks right so far)

EXPECTED: True
ACTUAL:   True
That's correct! (2 checks right so far)

EXPECTED: False
ACTUAL:   False
That's correct! (3 checks right so far)
  ...

#028 — Logic

10 checks passed

Solution

def starts_with_x_or_y(the_str):
  first_letter = the_str[0]
  #                      VV look at this!
  if first_letter == "x" or first_letter == "y":
    return "It does!"
  else:
    return "It does not."

def a_or_b(a, b):
  return a or b

def a_and_b(a, b):
  return a and b

def not_a(a):
  return not a

Output

Function: a_or_b
EXPECTED: True
ACTUAL:   True
That's correct! (1 checks right so far)

EXPECTED: True
ACTUAL:   True
That's correct! (2 checks right so far)

EXPECTED: True
ACTUAL:   True
That's correct! (3 checks right so far)
  ...

🔄

Collections & Loops

Lists, dictionaries, while/for loops, map, filter & summarise

10 files

#029 — Lists

Demo

Output

[1, 2, 3, 4, 5]

#030 — List Indexing

8 checks passed

Solution

def get_first_item(the_list):
  return the_list[0]

def get_last_item(the_list):
  return the_list[-1]

def get_nth_item(the_list, n):
  return the_list[n]

def get_items_between_one_and_three(the_list):
  return the_list[1:3]

Output

Function: get_first_item
EXPECTED: a
ACTUAL:   a
That's correct! (1 checks right so far)

EXPECTED: 34
ACTUAL:   34
That's correct! (2 checks right so far)


Function: get_last_item
EXPECTED: e
  ...

#031 — List Modification

12 checks passed

Solution

def append_item_to_list(the_list, item):
  the_list.append(item)
  return the_list

def remove_item_from_list(the_list, item):
  the_list.remove(item)
  return the_list

def count_items_in_list(the_list, item):
  return the_list.count(item)

def get_index_of_item(the_list, item):
  return the_list.index(item)

def reverse_list(the_list):
  the_list.reverse()
  return the_list

def list_length(the_list):
  return len(the_list)

Output

['a', 'b', 'c', 'd']
3
['a', 'b', 'c', 'd']
['a', 'b', 'c']
['a', 'b', 'c', 'd']

Function: append_item_to_list
EXPECTED: ['a', 'b', 'c']
ACTUAL:   ['a', 'b', 'c']
That's correct! (1 checks right so far)

EXPECTED: [3, 1, 6]
  ...

#032 — While Loops

2 checks passed

Solution

def add_cats_repeatedly(word_list, count):
  i = 0
  while i < count:
    word_list.append("cats")
    i = i + 1
  return word_list

Output

Hello, Kay!
The number is now 0
The number is now 1
The number is now 2
The number is now 3
The number is now 4
The number is now 5
The number is now 6
The number is now 7
The number is now 8
The number is now 9

  ...

#033 — For Loops

Demo

Solution

def print_numbers_in_range():
  for number in range(0, 10):
    print(f"This number is {number}")

def print_numbers_in_range_with_a_while():
  number = 0
  while number < 10:
    print(f"This number is {number}")
    number = number + 1

Output

This letter is a
This letter is b
This letter is c

#034 — Summarising

2 checks passed

Solution

def add_up_numbers(numbers):
  total = 0
  for number in numbers:
    total = total + number
  return total

Output

My King,
I need another five years.
Then your crab will be ready.
Sincerely,
Chuang-tzu


Function: add_up_numbers
EXPECTED: 10
ACTUAL:   10
That's correct! (1 checks right so far)

  ...

#035 — Mapping

2 checks passed

Solution

def add_one_hundred_to_numbers(numbers):
  result = []
  for number in numbers:
    result.append(number + 100)
  return result

Output

['I', 'need', 'another', 'five', 'years']
['I', 'n', 'a', 'f', 'y']

Function: add_one_hundred_to_numbers
EXPECTED: [101, 102, 103, 104]
ACTUAL:   [101, 102, 103, 104]
That's correct! (1 checks right so far)

EXPECTED: [102, 103, 104, 105]
ACTUAL:   [102, 103, 104, 105]
That's correct! (2 checks right so far)

#036 — Filtering

2 checks passed

Solution

def only_positive_numbers(numbers):
  result = []
  for number in numbers:
    if number > 0:
      result.append(number)
  return result

Output

[32, 40, None, 1, 32]
[32, 40, 1, 32]

Function: only_positive_numbers
EXPECTED: [4, 3]
ACTUAL:   [4, 3]
That's correct! (1 checks right so far)

EXPECTED: []
ACTUAL:   []
That's correct! (2 checks right so far)

#037 — Dicts

Demo

Output

A String is:
  A sequence of characters
A List is:
  A sequence of any item
A Dictionary is:
  A collection of keys mapped to values

#038 — Dict Operations

2 checks passed

Solution

def count_words_by_length(words):
  counts = {}
  for word in words:
    length = len(word)
    if length not in counts:
      counts[length] = 1
    else:
      counts[length] = counts[length] + 1
  return counts

Output

{'t': 2, 'h': 3, 'e': 4, ' ': 7, 'q': 1, 'u': 3, 'i': 1, 'c': 2, 'k': 1, 'b': 2, 'r': 3, 's': 1, 'j': 1, 'm': 1, 'p': 1, 'd': 1, 'o': 1, 'v': 1, 'l': 1, 'a': 2, 'z': 1, 'y': 1}

Function: count_words_by_length
EXPECTED: {3: 2, 1: 1, 4: 1}
ACTUAL:   {3: 2, 1: 1, 4: 1}
That's correct! (1 checks right so far)

EXPECTED: {4: 3, 3: 1}
ACTUAL:   {4: 3, 3: 1}
That's correct! (2 checks right so far)