Lab 6, Part 2: Strings with For Loops

Note: Some of you may have done parts of this during Lab05, if so, just skip ahead to functions that you have not yet written.

Handling strings

A necklace strung with 5 beads. Each bead has a letter on it, and the letters spell out C S 1 1 1.

Table of some string operations:

symbol operation example
+ concatenation str1 = 'I am '
str2 = 'your father '
darth = str1 + str2
yoda = str2 + str1
* repetition 'hee'*3 ==> 'heeheehee'
[] index str2[5]==> 'f'
[:] slice str2[2:5]==> 'ur '
in in 'dad' in str2 ==> False
'at' in str2 ==> True
not in not in str1 not in str2 ==> True
str1 not in darth ==> False

A couple of handy string tips:

Task 1. Writing string functions with loops

Create a new file called and add the functions below to that file.

Partner B
  1. Write a function called getWordValue(word) that takes in a word, and returns the value of the word using the following (made-up) rule: Each vowel (a,e,i,o,u) counts as 5 and each consonant counts as 1.

    • Here's an isVowel function that you can use (or, you can write your own):

      def isVowel(s):
          """returns True if s is a vowel; false otherwise"""
          lowercaseS = s.lower()
          return lowercaseS in 'aeiou'
    • Here are some test cases for your getWordValue function:
      print(getWordValue('hello')) ==> 13
      print(getWordValue('I')) ==> 5
      print(getWordValue('ouch')) ==> 12
      print(getWordValue('WELLESLEY')) ==> 21
      # Check that your code works on this one:
      print(getWordValue('Go 123 Wellesley!!!!')) ==> 27
Partner A
  1. Write a function called starify(word) that takes in a word, and returns a new string with a * after each letter in the original word. Hint: create a new string variable, initially empty, that will store the new string to be returned.

    print(starify('OMG')) ==> O*M*G*
    print(starify('wicked')) ==> w*i*c*k*e*d*
    print(starify('Starry')) ==> S*t*a*r*r*y*
  2. Write a function called betterStarify(word) that takes in a word, and returns a new string with a * after each letter in the original word, but not after the last letter in the word.
    print(betterStarify('OMG')) ==> O*M*G
    print(betterStarify('wicked')) ==> w*i*c*k*e*d
    print(betterStarify('Starry')) ==> S*t*a*r*r*y
Partner B
  1. In this task, you'll write two functions.
    Note that in the box below, you're given a predicate called starTime that returns True twenty percent of the time and False eighty percent of the time.
    You can copy/paste the starTime predicate below into your file:

    import random
    def starTime():
        """returns True 20% of the time; False otherwise.
        Note: random.random() returns a random number between 0 and 1
        return random.random() > 0.80
    • Write a fruitful function called makeOneRow that takes one parameter rowLength, and returns a string with length rowLength that is made up of stars (*) and dashes (-). When generating the row, you can use the starTime predicate so that 20% of the row is stars. For each spot in the row, use the predicate starTime: if it returns True, add a star to your row, otherwise, add a dash. Here are some sample invocations of makeOneRow:

      print(makeOneRow(20)) ==> -*------*--*----**--
      print(makeOneRow(20)) ==> ----*----*----------
      print(makeOneRow(20)) ==> ---***-*--**------*-
      print(makeOneRow(20)) ==> *--**----*--**--*---
    • Write another fruitful function called starrySky that takes two parameters: width and height. starrySky returns a string that contains a 'sky' that has width and height dimensions and each row is created by a call to makeOneRow. The sky is built by adding each row and a newline character (\n) at the end. Here are some sample invocations:
      print(starrySky(10, 10)) ==>
      print(starrySky(5, 50)) ==> 
      print(starrySky(3, 60)) ==> 
Partner A
  1. Write a predicate called lottaVowels(word) that returns True if the word contains more than 2 vowels. You may use the provided isVowel in your file.
    print(lottaVowels('OMG')) ==> False
    print(lottaVowels('hello')) ==> False
    print(lottaVowels('ABBA')) ==> False
    print(lottaVowels('GottaLOVEABBA')) ==> True
    print(lottaVowels('piano')) ==> True
    print(lottaVowels('eee')) ==> True
    print(lottaVowels('gummybears')) ==> True
    print(lottaVowels('laugh')) ==> False
    print(lottaVowels('laughingxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx')) ==> True

    Note: look at the last example, with this string 'laughingxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx'. It would be efficient if your lottaVowels returned True as soon as the third vowel was encountered, rather than waiting until the end of the string. Can you amend your lottaVowels so it does that? (Sometimes we call this 'early exit')

Partner A
  1. Write a function called checkPassword(word) that takes in a word, and returns True if the word satisfies the following password criteria and False otherwise. Hint: Python has some very useful built-in functions such as islower,isupper and isdigit, for example 'a'.islower() returns True and 'a'.isupper() returns False.
    • Password must contain a mix of upper and lower case letters
    • Password must contain at least 1 number
    • Password must contain at least 1 special character from this set !#$%&*
      print(checkPassword('hello123')) ==> False
      print(checkPassword('PASSWORD')) ==> False
      print(checkPassword('myPASSWORD?')) ==> False
      print(checkPassword('loveMyDogCharlie!')) ==> False
      print(checkPassword('CS111#rocksmyworld')) ==> True
      print(checkPassword('running99*FAST')) ==> True
      print(checkPassword('oK8!')) ==> True # Minimum length would be good idea too
Partner B
  1. [OPTIONAL] Write a function called ransomNote(sentence) that takes in a sentence, and returns a new sentence, based on the original sentence, with each letter randomly capitalized (with a 50% chance of being capitalized. Might need to use the random.randint function). Need a randint() refresher? Here is an example from the previous lab with the coin flip, and here are the general python documentation pages for random numbers.
    print(ransom("Must provide chocolate to get your teddy bear back")) ==>
    muST ProvIDE CHocOlATe To get YOur TEddY bEAr bACK
    print(ransom("Meet me at grand central station with harry styles and a million dollars tonight")) ==>
    mEET mE at graND CentRAL sTatIOn WITh HarRY StYlEs AND a mIlLIOn DOLLaRs TOnigHT

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