Lab 6: Strings with For Loops

Handling strings

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:

• yourString[-1] returns the last letter of a string, eg 'hello'[-1] ==> 'o'
• .lower() returns a lowercase version of the given string, eg 'HeLLo.lower() ==> 'hello'

String functions with loops

Create a file named lab06.py for this part of the lab.

betterStarify

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')) # should print O*M*G
print(betterStarify('wicked')) # should print w*i*c*k*e*d
print(betterStarify('Starry')) # should print S*t*a*r*r*y

hasDoubleVowel

Write a predicate called hasDoubleVowel that takes a word as its only parameter, and returns True if the word has two of the same vowel in a row, or False if it doesn't. For example, it should return True for eel and pool but False for feather and tell ('feather' has two vowels in a row, but they're not the same vowel; 'tell' has two of the same letter in a row, but they're not vowels).

• 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"""
      return len(s) == 1 and s.lower() in 'aeiou'

• Here are some test calls you can copy into the shell:

  hasDoubleVowel('eel') # should be True
  hasDoubleVowel('pool') # should be True
  hasDoubleVowel('breadroot') # should be True
  hasDoubleVowel('kelp') # should be False
  hasDoubleVowel('feather') # should be False
  hasDoubleVowel('knight') # should be False
  hasDoubleVowel('oreo') # should be False

Feeling lost? Click here for a hint!

For this problem, an index loop is helpful, since it allows you to refer to a previous or upcoming letter in addition to the letter at the current index within the loop (just subtract or add 1 to the index). Just be careful to either start at index 1 or stop before the normal final index so that you don't try to access a letter before the beginning or after the end of the word.

starryRow and starrySky

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 (and add the import while you're at it):

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 starryRow 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 (on average). 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 starryRow:

print(starryRow(20)) # might print -*------*--*----**--
print(starryRow(20)) # might print ----*----*----------
print(starryRow(20)) # might print ---***-*--**------*-
print(starryRow(20)) # might print *--**----*--**--*---

Now 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 starryRow. The sky is built by adding each row and a newline character (\n) at the end. Here are some sample invocations along with what their output might look like:

print(starrySky(10, 10))
*-------*-
--*-------
----------
---**-----
**--*--*--
--------*-
----------
-----*----
------*---
--*-------
print(starrySky(5, 50))
----------------**-----**-*----------*---------*--
*--*----*---*---*-----**------*------------*--*---
-*---*---*--------*----------**--------*---*--*---
---**----*-**---------**---*-------**--*-------*--
------**-----------------*--------*-----*---*--*--
print(starrySky(3, 60))
--------*-**-**---*---*---------*--*--**-------------------*
----*---------*--*-*--*-**---*----*--------*---*-*----*----*
----*---------*--*-*--*-**---*----*--------*---*-*----*----*

funnyVoice

Write a function called funnyVoice that takes in a sentence as a parameter, and returns a new sentence, based on the original sentence, with each letter randomly capitalized (with a 50% chance of being capitalized. You will need to use the random.randint and/or random.random functions. Use those links to read our quick-reference documentation for a refresher if you need to.

Here are the general python documentation pages for random numbers if you're curious about more details.

print(funnyVoice("Hello"))
# might print: heLlO
print(funnyVoice("SpongeBob SquarePants"))
# might print: sPOnGeBOB sqUArepANtS

Table of Contents

• Lab 6 Home
• Part 1: Debugging Loops
• Part 2: Exercises
• Extra Practice: Loops with Strings (for loops)
• Extra Practice: HiLo Game (while loops)
• Extra Practice: Loops and Graphics
• Knowledge Check