Tutorial 6

1. Every letter counts

   First up a problem to give you a little practice working with the collection types (lists and dictionaries). Write the following implementations of the function letter_frequency that takes a string and returns a collection type showing how often each letter of the alphabet occurs in the string.

   a. The first version (letter_frequencyA) should return a list with 26 integer elements representing the frequency of occurrence of each letter of the alphabet in order from a to z.

   b. The second version (letter_frequencyB) should return a list of 26 lists, each of which contains a letter and its associated count.

   c. The third version (letter_frequencyC) should return a dictionary that uses the letters as keys and whose values are the letters' counts. Make sure to use a dictionary specific solution!

   The program that will call these functions is letter_frequency.py. Your job is to replace the pass statements with function bodies that implement the functionality specified above. Studying the embedded tests should answer any other questions you have about the functions' operations.