Deck 3: Codes and Other Secrets: String Operators and Methods, the Len Built-In Function, Keyword Parameters, User Input

Question 1

What is the string concatenation operator in Python?

A) :
B) +
C) ~
D) *

Answer 1

B

Question 2

What is the repetition operator in Python?

A) :
B) +
C) ~
D) *

Answer 2

D

Question 3

What is the value of 'John'[0]?

A) J
B) 'J'
C) 0
D) Undefined

Answer 3

B

Question 4

What function returns the number of characters in a string?

A) range
B) length
C) leng
D) stringlen

Question 5

Case Study 1:
1. >>> name = "Roy G Biv"
2. >>> first = name[0]
3. >>> first
4. >>> middleChar = name[4]
5. >>> middleChar
6. >>> name[-1]
-Refer to the session in the accompanying Case Study 1. What is printed after line 3?

A) 'R'
B) R
C) 'v'
D) G

Question 6

Case Study 1:
1. >>> name = "Roy G Biv"
2. >>> first = name[0]
3. >>> first
4. >>> middleChar = name[4]
5. >>> middleChar
6. >>> name[-1]
-Refer to the session in the accompanying case study 1. What is printed after line 6?

A) 'R'
B) R
C) 'v'
D) G

Question 7

What is the [:] operator called?

A) Cut
B) Index
C) Slice
D) Substring

Question 8

What is the result of the following code?
'bc' in 'abc'

A) True
B) False
C) 'a'
D) 1

Question 9

What method can be used to surround a string with spaces in order to make it a certain length?

A) replace
B) count
C) upper
D) center

Question 10

What function converts a character to its Unicode equivalent?

A) str
B) chr
C) ord
D) num

Question 11

Case Study 2:
1. def scramble2Encrypt(plainText):
2. evenChars = ""
3. oddChars = ""
4. charCount = 0
5. for ch in plainText:
6. if charCount % 2 == 0:
7. evenChars = evenChars + ch
8. else:
9. oddChars = oddChars + ch
10. charCount = charCount + 1
11. cipherText = oddChars + evenChars
12. return cipherText
-Refer to the code in the accompanying case study 2. What is the name of the % operator used on line 6?

A) Division
B) Modulo
C) Cipher
D) Rail fence

Question 12

Case Study 2:
1. def scramble2Encrypt(plainText):
2. evenChars = ""
3. oddChars = ""
4. charCount = 0
5. for ch in plainText:
6. if charCount % 2 == 0:
7. evenChars = evenChars + ch
8. else:
9. oddChars = oddChars + ch
10. charCount = charCount + 1
11. cipherText = oddChars + evenChars
12. return cipherText
-Refer to the code in the accompanying case study 2. What type of cipher has been implemented?

A) Transposition
B) Accumulator
C) Substitution
D) Vignère

Question 13

Python uses the ____ function to ask the user for a single string.

A) string
B) get
C) input
D) prompt

Question 14

When implementing a substitution cipher in Python, use the ____ method to return the position of any letter in the alphabet.

A) range
B) len
C) position
D) index

Question 15

When implementing the Vigenère cipher, which step comes first?

A) Use the accumulator pattern to add the ciphertext letter to the ciphertext message.
B) Determine which letter of the key we should use.
C) Return the string as the ciphertext message.
D) Look up the ciphertext letter in the Vigenère square, using the key letter row and plaintext character column.

Question 16

The concatenation operator joins two strings and adds a space between them.

Question 17

Although the function call len('abc') returns 3, we would use 'abc'[2] to access the character 'c'.

Question 18

The find method finds the number of occurrences of one string within another.

Question 19

The letter 'a' corresponds to the number 0 in the Unicode system.

Question 20

The process of turning ciphertext into plaintext is called decryption.

Question 21

Match each line of code with a result below. Assume aString is initialized as below:
aString = "golden gopher football"
-aString.count('o')

A) 4
B) 18
C) 0
D) 1

Question 22

Match each line of code with a result below. Assume aString is initialized as below:
aString = "golden gopher football"
-aString.find('b')

A) 5
B) 19
C) 1
D) 2

Question 23

Match each line of code with a result below. Assume aString is initialized as below:
aString = "golden gopher football"
-aString.index('g')

A) 6
B) 20
C) 2
D) 3

Question 24

Match each line of code with a result below. Assume aString is initialized as below:
aString = "golden gopher football"
-aString.count('oo')

A) 7
B) 21
C) 3
D) 4

Question 25

What does the term "string" refer to in computer science language, and how is a string defined in Python?

Question 26

What is the operator represented by the * in the following code? Explain its use.
>>> 'go'*3

Question 27

Describe the functionality of the string index operator with an example.

Question 28

One of the easiest ways to encrypt a message is to simply scramble the letters. For example, the word "mango" could be randomly transformed to "nogma." In fact, there are 120 different possible arrangements of the word "mango." Explain why this is not an effective encryption method.

Question 29

Case Study 2:
1. def scramble2Encrypt(plainText):
2. evenChars = ""
3. oddChars = ""
4. charCount = 0
5. for ch in plainText:
6. if charCount % 2 == 0:
7. evenChars = evenChars + ch
8. else:
9. oddChars = oddChars + ch
10. charCount = charCount + 1
11. cipherText = oddChars + evenChars
12. return cipherText
-Refer to the code in the accompanying Case Study 2. Provide a line-by-line description of what is happening on lines 5 through 10.

Question 30

Case Study 2:
1. def scramble2Encrypt(plainText):
2. evenChars = ""
3. oddChars = ""
4. charCount = 0
5. for ch in plainText:
6. if charCount % 2 == 0:
7. evenChars = evenChars + ch
8. else:
9. oddChars = oddChars + ch
10. charCount = charCount + 1
11. cipherText = oddChars + evenChars
12. return cipherText
-Refer to the code in the accompanying Case Study 2. Explain how you would reverse the process of scramble2Encrypt in order to decrypt the message.

Question 31

What is the advantage of a substitution cipher over a transposition cipher?

Question 32

How effective is a brute force approach to cracking a substitution cipher? Explain your answer.

Question 33

Provide a high-level summary of the actions needed to encrypt a message using a Vigenère square.