Chapter 9 Exercises

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

   # STEP 1: INITIALIZE ACCUMULATOR newString = "" # STEP 2: GET DATA Phrase = "Rubber baby buggy bumpers. # STEP 3: LOOP THROUGH THE DATA for letter in phrase # STEP 4: ACCUMULATE newString = newString letter # STEP 5: PROCESS RESULT print(newString

   Change Phrase to phrase and add a " at the end of the line. Add a : at the end of line 6. Add a + in line 8. Add a ) at the end of line 10.

   # STEP 1: INITIALIZE ACCUMULATOR newString = "" # STEP 2: GET DATA phrase = "Rubber baby buggy bumpers." # STEP 3: LOOP THROUGH THE DATA for letter in phrase: # STEP 4: ACCUMULATE newString = newString + letter # STEP 5: PROCESS RESULT print(newString)

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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 newString = "" # STEP 2: GET DATA phrase = "This is a string." # STEP 3: LOOP THROUGH THE DATA for letter in phrase: # STEP 4: ACCUMULATE newString = letter + newString # STEP 5: PROCESS RESULT print(newString)

   In line 3, newString should equal newString + letter + " ". The order does matter.

   # STEP 1: INITIALIZE ACCUMULATOR newString = "" # STEP 2: GET DATA phrase = "This is a string." # STEP 3: LOOP THROUGH THE DATA for letter in phrase: # STEP 4: ACCUMULATE newString = newString + letter + " " # STEP 5: PROCESS RESULT print(newString)

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3. Fix the indention on 4 lines below to correctly print the reverse of the string. It should print: “!yadhtriB yppaH.”

   # STEP 1: INITIALIZE ACCUMULATORS newString = "" # STEP 2: GET DATA phrase = "Happy Birthday!" # STEP 3: LOOP THROUGH THE DATA for letter in phrase: # STEP 4: ACCUMULATE newString = letter + newString # STEP 5: PROCESS RESULT print(newString)

   Change the indention on lines 4, 7, 8, and 10 as shown below.

   # STEP 1: INITIALIZE ACCUMULATORS newString = "" # STEP 2: GET DATA phrase = "Happy Birthday!" # STEP 3: LOOP THROUGH THE DATA for letter in phrase: # STEP 4: ACCUMULATE newString = letter + newString # STEP 5: PROCESS RESULT print(newString)

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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: newString = "" # STEP 4: ACCUMULATE newString = newString + phrase # STEP 5: PROCESS RESULT print(phrase)

   newString should be initialized outside of the for loop. Inside the for loop, it should equal letter + newString and the print statement should be outside the for loop and it should print the newString

   # STEP 1: INITIALIZE ACCUMULATORS newString = "" # STEP 2: GET DATA phrase = "Hey look, I'm a string!" # STEP 3: LOOP THROUGH THE DATA for letter in phrase: # STEP 4: ACCUMULATE newString = letter + newString # STEP 5: PROCESS RESULT print(newString)

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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 newString = # STEP 2: GET DATA phrase = "This is a test" # STEP 3: LOOP THROUGH THE DATA for l in phrase: # STEP 4: ACCUMULATE newString = letter + newString letter # STEP 5: PROCESS RESULT print()

   Initialize newString to the empty string in line 2. Change l to letter in line 6. Add a + in line 8. Add newString on line 10.

   # STEP 1: INITIALIZE ACCUMULATOR newString = "" # STEP 2: GET DATA phrase = "This is a test" # STEP 3: LOOP THROUGH THE DATA for letter in phrase: # STEP 4: ACCUMULATE newString = letter + newString + letter # STEP 5: PROCESS RESULT print(newString)

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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 newString = "" # 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 newString = newString + letter + letter # STEP 5: PROCESS RESULT print(newString)

   Change line 4 to be newString = letter + newString + newString

   # STEP 1: INITIALIZE ACCUMULATOR newString = "" # 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 newString = letter + newString + letter # STEP 5: PROCESS RESULT print(newString)

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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.”

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

   Add line 5 as shown below.

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

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

   # STEP 1: INITIALIZE ACCUMULATOR newString = " " # 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 + newString # STEP 5: PROCESS RESULT print(newString)

   newString should not be initialized with spaces. On line 3, it should be “for letter in phrase:”. Line 4 should be “newString = newString + letter”.

   # STEP 1: INITIALIZE ACCUMULATOR newString = "" # STEP 2: GET DATA phrase = "I'm just a string." # STEP 3: LOOP THROUGH THE DATA for letter in phrase: # STEP 4: ACCUMULATE newString = newString + letter # STEP 5: PROCESS RESULT print(newString)

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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" str = "abcdefghijklmnopqrstuvwxyz. eStr = zyxwvutsrqponmlkjihgfedcba ." encodedMessage = message for letter in message pos = str.find(letter) encodedMessage = encodedMessage + eStr[pos:pos+1] print encodedMessage)

   Change line 2 to end in ". Change line 3 to start the string with ". Change line 4 to set encodeMesage to the empty string to start. Add : at the end of line 5. Add ( on line 8.

   message = "meet me at midnight" str = "abcdefghijklmnopqrstuvwxyz. " eStr = "zyxwvutsrqponmlkjihgfedcba ." encodedMessage = "" for letter in message: pos = str.find(letter) encodedMessage = encodedMessage + eStr[pos:pos+1] print(encodedMessage)

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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”.

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

    At the end of the body of the while loop, make sure to find the “1” again.

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

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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 newString = "" # STEP 2: GET DATA phrase = "Happy Birthday!" # STEP 3: LOOP THROUGH THE DATA for letter in phrase: # STEP 4: ACCUMULATE newString = letter + newString # STEP 5: PROCESS RESULT print(newString)

    Define the function as shown below. Call the function and print the result.

    def reverse(phrase): # STEP 1: INITIALIZE ACCUMULATORS newString = "" # STEP 3: LOOP THROUGH THE DATA for letter in phrase: # STEP 4: ACCUMULATE newString = letter + newString # STEP 5: PROCESS RESULT return(newString) print(reverse("Happy Birthday!"))

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

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

    In line 2, make sure to find the position of the misspelled word. In line 4, str = str[0:pos] + "received" + str[pos+len("recieved"):len(str)].

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

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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 newString = "" # STEP 2: GET DATA phrase = "This is a test" # STEP 3: LOOP THROUGH THE DATA for letter in phrase: # STEP 4: ACCUMULATE newString = letter + newString + letter # STEP 5: PROCESS RESULT print(newString)

    Define the function as shown below. Call the function and print the result.

    def mirror(phrase): # STEP 1: INITIALIZE ACCUMULATOR newString = "" # STEP 3: LOOP THROUGH THE DATA for letter in phrase: # STEP 4: ACCUMULATE newString = letter + newString + letter # STEP 5: PROCESS RESULT return(newString) print(mirror("Hi Class!"))

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

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

    On line 2, use the find method to find the period. On line 3, pos should be greater than or equal to 0. Line 4 should be “str = str[0:pos] + “,” + str[pos+len(“.”):len(str)]” and line 5 should find the next period.

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

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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" str = "abcdefghijklmnopqrstuvwxyz. " eStr = "zyxwvutsrqponmlkjihgfedcba ." encodedMessage = "" for letter in message: pos = str.find(letter) encodedMessage = encodedMessage + eStr[pos:pos+1] print(encodedMessage)

    Define the function as shown below and be sure to return the encoded string. Call the function and print the result.

    def encode(message): str = "abcdefghijklmnopqrstuvwxyz. " eStr = "zyxwvutsrqponmlkjihgfedcba ." encodedMessage = "" for letter in message: pos = str.find(letter) encodedMessage = encodedMessage + eStr[pos:pos+1] return(encodedMessage) print(encode("The password is touchdown."))

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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 reverseString = "" mirrorString = " " # STEP 2: GET DATA phrase = "This is the string" # STEP 3: LOOP THROUGH THE DATA for phrase in phrase: # STEP 4: ACCUMULATE reverseString = reverseString + letter mirrorString = letter + letter + reverseString # STEP 5: PROCESS RESULT print(reverseString) print(mirrorString)

    mirrorString in line 2 should not be set equal to a string of a space. The for loop should be “for letter in phrase”. reverseString should equal letter + reverseString and mirrorString should equal letter + mirrorString + letter.

    def aProcedure(phrase): # STEP 1: INITIALIZE ACCUMULATOR reverseString = "" mirrorString = "" # STEP 3: LOOP THROUGH THE DATA for letter in phrase: # STEP 4: ACCUMULATE reverseString = letter + reverseString mirrorString = letter + reverseString + letter # STEP 5: PROCESS RESULT print(reverseString) print(mirrorString) phrase = "This is the string" aProcedure(phrase)

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17. Modify the code below to create a function that returns the decoded input string. It should print: “meet me at midnight.”

    message = "" str = "abcdefghijklmnopqrstuvwxyz. " eStr = "zyxwvutsrqponmlkjihgfedcba ." encodedMessage = "nvvg.nv.zg.nrwmrtsg" for letter in encodedMessage: pos = eStr.find(letter) message = message + str[pos:pos+1] print(message)

    Define the function as shown below. Be sure to return the decoded message. Call the function and print the result.

    def decode(eMessage): message = "" str = "abcdefghijklmnopqrstuvwxyz. " eStr = "zyxwvutsrqponmlkjihgfedcba ." for letter in eMessage: pos = eStr.find(letter) message = message + str[pos:pos+1] return(message) print(decode("nvvg.nv.zg.nrwmrtsg"))

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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 newString = "" aString = "" # STEP 2: GET DATA phrase = "This is a mirror!"

    # STEP 1: INITIALIZE ACCUMULATOR newString = "" aString = "" # STEP 2: GET DATA phrase = "This is a mirror!" # STEP 3: LOOP THROUGH THE DATA for letter in phrase: # STEP 4: ACCUMULATE newString = letter + newString for letter in newString: aString = letter + aString + letter # STEP 5: PROCESS RESULT print(aString)

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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.

    Create a function similar to the encode function above, but change it to take two input values.

    def encode2(message, eStr): str = "abcdefghijklmnopqrstuvwxyz. " encodedMessage = "" for letter in message: pos = str.find(letter) encodedMessage = encodedMessage + eStr[pos:pos+1] return(encodedMessage) print(encode2("This is a test", "zyxwvutsrqponmlkjihgfedcba ."))

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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" str = "abcdefghijklmnopqrstuvwxyz. " eStr = "zyxwvutsrqponmlkjihgfedcba ." encodedMessage = "" for letter in message: pos = str.find(letter) encodedMessage = encodedMessage + eStr[pos:pos+1] print(encodedMessage)

    Initialize decodedMessage and then iterate through encodedMessage and in the body of the for loop, just switch eStr and str from the encoded message.

    message = "meet me at midnight" str = "abcdefghijklmnopqrstuvwxyz. " eStr = "zyxwvutsrqponmlkjihgfedcba ." encodedMessage = "" for letter in message: pos = str.find(letter) encodedMessage = encodedMessage + eStr[pos:pos+1] print(encodedMessage) decodedMessage = "" for letter in encodedMessage: pos = eStr.find(letter) decodedMessage = decodedMessage + str[pos:pos+1] print(decodedMessage)

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