MITx 6.00.1x Python Notes: Counting Letters

Problem 1: Counting Vowels
Assume s is a string of lower case characters. Write a program that counts up the number of vowels contained in the string s. Valid vowels are: 'a', 'e', 'i', 'o', and 'u'. For example, if s = 'azcbobobegghakl', the program should print:

Number of vowels: 5

Python code

Problem 2: Counting Bobs
Write a program that prints the number of times the string 'bob' occurs in s. For example, if s = 'azcbobobegghakl', then the program should print:

Number of times bob occurs is: 2

Python code

Problem 3: Alphabetical Substrings
Write a program that prints the longest substring of s in which the letters occur in alphabetical order. For example, if s = 'azcbobobegghakl', then the program should print:

Longest substring in alphabetical order is: beggh

Python code