Encryption basics in Intro to Computing - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to encrypt a message by shifting each letter by 3 positions.

Intro to Computing

def encrypt(message):
    result = ""
    for char in message:
        if char.isalpha():
            shifted = chr((ord(char) - 65 + [1]) % 26 + 65)
            result += shifted
        else:
            result += char
    return result

Drag options to blanks, or click blank then click option'

A0

B1

C5

D3

Attempts:

3 left

💡 Hint

Common Mistakes

Using 0 means no encryption happens.

Using 1 or 5 shifts letters incorrectly for this example.

Shifting letters by 3 positions is a common simple encryption called Caesar cipher.

2fill in blank

medium

Complete the code to decrypt a message encrypted by shifting letters by 3 positions.

Intro to Computing

def decrypt(message):
    result = ""
    for char in message:
        if char.isalpha():
            shifted = chr((ord(char) - 65 - [1]) % 26 + 65)
            result += shifted
        else:
            result += char
    return result

Drag options to blanks, or click blank then click option'

A3

B5

C1

D0

Attempts:

3 left

💡 Hint

Common Mistakes

Using 0 means no change, so message stays encrypted.

Using a different number than encryption causes wrong output.

Decrypting reverses the encryption by shifting letters backward by the same number.

3fill in blank

hard

Fix the error in the code to correctly check if a character is uppercase before encrypting.

Intro to Computing

def encrypt(message):
    result = ""
    for char in message:
        if [1]:
            shifted = chr((ord(char) - 65 + 3) % 26 + 65)
            result += shifted
        else:
            result += char
    return result

Drag options to blanks, or click blank then click option'

Achar.isalpha()

Bchar.isupper()

Cchar.isdigit()

Dchar.islower()

Attempts:

3 left

💡 Hint

Common Mistakes

Using isalpha() includes lowercase letters which may cause wrong shifts.

Using isdigit() or islower() is incorrect for uppercase check.

We only want to shift uppercase letters, so we check if the character is uppercase.

4fill in blank

hard

Fill both blanks to create a dictionary comprehension that maps each letter to its encrypted form by shifting 2 positions.

Intro to Computing

encrypted_dict = {char: chr((ord(char) - 65 [1] 2) % 26 + 65) for char in 'ABCDEFGHIJKLMNOPQRSTUVWXYZ' if char [2] 'M'}

Drag options to blanks, or click blank then click option'

A+

B-

C<

D>

Attempts:

3 left

💡 Hint

Common Mistakes

Using '-' in the first blank shifts letters backward.

Using '>' in the second blank selects letters after 'M'.

The first blank needs '+' to shift letters forward by 2. The second blank uses '<' to filter letters before 'M'.

5fill in blank

hard

Fill all three blanks to create a dictionary comprehension that maps lowercase letters to uppercase encrypted letters shifted by 1, only for letters greater than 'f'.

Intro to Computing

encrypted_lower = { [1]: [2] for [3] in 'abcdefghijklmnopqrstuvwxyz' if [3] > 'f' }

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A{char.upper()}

Bchar.upper()

Cchar

Dchr((ord(char.upper()) - 65 + 1) % 26 + 65)

Attempts:

3 left

💡 Hint

Common Mistakes

Using string interpolation in the key instead of a variable.

Not using the correct dictionary comprehension syntax.

The dictionary comprehension syntax requires a key-value pair separated by ':'. The key is 'char', the value is the encrypted uppercase letter shifted by 1.