Chapter 9 Exercises¶

1. Fix 5 errors in code below to correctly print: “Rubber baby buggy bumpers.”

   # Step 1: Initialize accumulator new_string = "" # Step 2: Get data Phrase = "Rubber baby buggy bumpers. # Step 3: Loop through the data for letter in phrase # Step 4: Accumulate new_string = new_string letter # Step 5: Process result print(new_string

2. The code currently prints the reverse of a string. Change it so that it prints the string in the correct order, but every character is separated by a space (there should even be a space between a space and the next character).

   # Step 1: Initialize accumulator new_string = "" # Step 2: Get data phrase = "This is a string." # Step 3: Loop through the data for letter in phrase: # Step 4: Accumulate new_string = letter + new_string # Step 5: Process result print(new_string)

3. Fix the indention on 3 lines below to correctly print the reverse of the string. It should print: “!yadhtriB yppaH.”

   # Step 1: Initialize accumulator new_string = "" # Step 2: Get data phrase = "Happy Birthday!" # Step 3: Loop through the data for letter in phrase: # Step 4: Accumulate new_string = letter + new_string # Step 5: Process result print(new_string)

4. Fix the errors in the code to correctly print the reverse of the string. It should print: “!gnirts a m’I ,kool yeH”

   # Step 2: Get data phrase = "Hey look, I'm a string!" # Step 3: Loop through the data for letter in phrase: new_string = "" # Step 4: Accumulate new_string = new_string + phrase # Step 5: Process result print(phrase)

5. Fix 4 errors in the code below to correctly print the mirror of the text in phrase. It should print: “tset a si sihTThis is a test.”

   # Step 1: Initialize accumulator new_string = # Step 2: Get data phrase = "This is a test" # Step 3: Loop through the data for l in phrase: # Step 4: Accumulate new_string = letter + new_string letter # Step 5: Process result print()

6. The code currently prints each letter of the string twice in a row. Change it so that it prints the mirror of the string. It should print: “!rorrim a ni gnikool ekil s’tIIt’s like looking in a mirror!”

   # Step 1: Initialize accumulator new_string = "" # Step 2: Get data phrase = "It's like looking in a mirror!" # Step 3: Loop through the data for letter in phrase: # Step 4: Accumulate new_string = new_string + letter + letter # Step 5: Process result print(new_string)

7. The code below is supposed to replace all 1’s with i’s, but it is in an infinite loop. You can reload the page to stop the infinite loop. Add a line to make the code work. It should print: “This is a string.”

   a_str = "Th1s is a str1ng" pos = a_str.find("1") while pos >= 0: a_str = a_str[0:pos] + "i" + a_str[pos+1:len(str)] print(a_str)

8. Fix the errors so that the code prints “I’m just a string.”

   # Step 1: Initialize accumulator new_string = " " # Step 2: Get data phrase = "I'm just a string." # Step 3: Loop through the data for phrase in letter # Step 4: Accumulate letter = letter + new_string # Step 5: Process result print(new_string)

9. The program below is supposed to encode the text in message, but it has 5 errors. Fix the errors so that it prints: “nvvg.nv.zg.nrwmrtsg.”

   message = "meet me at midnight" a_str = "abcdefghijklmnopqrstuvwxyz. e_str = zyxwvutsrqponmlkjihgfedcba ." encoded_message = message for letter in message pos = a_str.find(letter) encoded_message = encoded_message + e_str[pos:pos+1] print encoded_message)

10. The code currently prints “This is a striniThis is a string”. Fix the error so that it replaces every “1” with “i” and prints “This is a string”.

    a_str = "Th1s is a str1ng" pos = a_str.find("1") while pos >= 0: pos = a_str.find("1") a_str = a_str[0:pos] + "i" + a_str[pos+1:len(a_str)] print(a_str)

11. Rewrite the following code to create a function that takes a string and returns the reverse of the string. It should print: “!yadhtriB yppaH.”

    # Step 1: Initialize accumulators new_string = "" # Step 2: Get data phrase = "Happy Birthday!" # Step 3: Loop through the data for letter in phrase: # Step 4: Accumulate new_string = letter + new_string # Step 5: Process result print(new_string)

12. Fix the errors in the code so that it replaces the misspelled word “recieved” with the correct spelling “received”

    a_str = "He recieved candy" pos = a_str.find("received") while pos >= 0: a_str = a_str[0:pos+len("recieved")] + "received" + a_str[pos:len(str)] pos = a_str.find("recieved") print(a_str)

13. Rewrite the following code to create a function that takes a string and returns the mirror of the string. It should print: “!ssalC iHHi Class!”.

    # Step 1: Initialize accumulator new_string = "" # Step 2: Get data phrase = "This is a test" # Step 3: Loop through the data for letter in phrase: # Step 4: Accumulate new_string = letter + new_string + letter # Step 5: Process result print(new_string)

14. Complete the code to change all the periods to commas.

    a_str = "I like to eat. sleep. learn. and code!" pos = a_str. while pos >= : a_str = a_str[0:pos] + + a_str[ :len(a_str)] pos = print(str)

15. Modify the code below to create a function that will that will take a message and return an encoded message. It should print: “nvvg.nv.zg.nrwmrtsg.”

    message = "meet me at midnight" a_str = "abcdefghijklmnopqrstuvwxyz. " e_str = "zyxwvutsrqponmlkjihgfedcba ." encoded_message = "" for letter in message: pos = a_str.find(letter) encoded_message = encoded_message + e_str[pos:pos+1] print(encoded_message)

16. Rewrite and fix the errors in the code to be a procedure that takes in a string and prints the reverse of the string and the mirror of the string. Make sure to call the procedure.

    # Step 1: Initialize accumulator reverse_string = "" mirror_string = " " # Step 2: Get data phrase = "This is the string" # Step 3: Loop through the data for phrase in phrase: # Step 4: Accumulate reverse_string = reverse_string + letter mirror_string = letter + letter + reverse_string # Step 5: Process result print(reverse_string) print(mirror_string)

17. Modify the code below to create a function decode(encoded_message) that takes the encoded message as an argument and returns the decoded string. It should return: “meet me at midnight” when called with “nvvg.nv.zg.nrwmrtsg”, and you should print this returned value.

    message = "" a_str = "abcdefghijklmnopqrstuvwxyz. " e_str = "zyxwvutsrqponmlkjihgfedcba ." encoded_message = "nvvg.nv.zg.nrwmrtsg" for letter in encoded_message: pos = e_str.find(letter) message = message + a_str[pos] print(message)

18. Finish the code so that it prints the mirror of the string with the correct way then the reverse. It should print: “This is a mirror!!rorrim a si sihT”

    # Step 1: Initialize accumulator new_string = "" a_string = "" # Step 2: Get data phrase = "This is a mirror!"

19. Create another function that encodes a string. Pass in both the string to be encoded and the string to use to encode the string as well.

20. Here’s the code to encode a message. Write code underneath it to decode the encoded message and print it.

    message = "meet me at midnight" a_str = "abcdefghijklmnopqrstuvwxyz. " e_str = "zyxwvutsrqponmlkjihgfedcba ." encoded_message = "" for letter in message: pos = a_str.find(letter) encoded_message = encoded_message + e_str[pos] print(encoded_message)