Practice Problems 2 For the week of 2020-02-17

The following exercises provide additional practice problems (not to turn in) for our material this week. Try to solve each problem on paper / whiteboard first before using Thonny to confirm your answers. You are encouraged to work on these practice exercises with classmates throughout the week.

1. Each of the following loops is an attempt to sum up the numbers from 1 to n, e.g.1+2+ ... +n (you can assume n is initialized to some value). For each case, explain why the code doesn’t actually sum the numbers 1 through n.

   a.

    sum = 0
    for i in range(n):
        sum = sum + i
   

   b.

    sum = 0
    for i in range(n):
        temp = sum + (i+1)
    sum = temp
   

   c.

    sum = 0
    for i in range(n):
        sum = (i+1)
   

   d.

    sum = 0
    for i in range(n):
        temp = (i+1)
        sum = temp
   

2. Write a function named factorial that has a single parameter, an integer n, and returns n!, i.e. 1*2*3* ... n.

3. Write a docstring for the following function

    def mystery():
        for i in range(5):
            print(2 + 2*i)
   

4. Write a function named rand_time that returns a random valid time in HH:MM format as a string. The result can have only a single hour digit, i.e. 1:01 and 10:15 are valid results, but must have two minutes digits, i.e. 1:1 is not a valid result. As a trickier extension, adapt your function to always generate two hour digits, i.e. 1:01 should be represented as 01:01.