Homework 9: Dictionaries

Suppose that the following dictionary is created, which indicates the (made up) number of currently declared majors in some Natural Sciences departments:

d = {'CHEM': 19, 'CSCI': 37, 'MATH': 23, 'PHYS': 13}

1. What are each of the following values?

   • d['MATH']
   • d['CSCI']
   • d['CHEM'] / 2

2. You learn that three new students have declared Computer Science as their major. How could you update the dictionary? Write actual code to do this!

3. If there are 15 Biology majors, how would you update the dictionary?

4. Using the original version of d = {'CHEM': 19, 'CSCI': 37, 'MATH': 23, 'PHYS': 13} above, what would be the value of c after the following code runs?

    c = 0
    for k in d:
      if 'H' in k:
        c += d[k]
   

Now, write two functions:

• The first function, vowel_histogram(s: str) -> dict[str,int], should return a dictionary where the keys are vowels (a, e, i, o, u) and the values are the number of occurrences of each vowel in the string. Here is an example of calling the function in the console:

    >>> vowel_histogram('This restaurant is a long way from our house.')
    {'a': 4, 'e': 2, 'i': 2, 'o': 4, 'u': 3}
  

• The second function, min_key(d: dict[str, int]) -> str, should return the key in the dictionary with the smallest corresponding value. Here is an example of calling the function in the console:

    >>> min_key({'a': 4, 'b': -5, 'c': 2, 'd': -7, 'e': 4})
    'd'
  

  In this example, the answer is 'd', because it is the key associated with the smallest value (-7). If the smallest value happens to occur more than once, your function may return any key associated with that value.