Exercises

Here are some exercises for you to try on your own. Solutions are available at http://pragprog.com/titles/gwpy3/practical-programming.

1. Two of Python’s built-in functions are min and max. In the Python shell, execute the following function calls:

   1. min(2, 3, 4)
   2. max(2, -3, 4, 7, -5)
   3. max(2, -3, min(4, 7), -5)

2. For the following function calls, in what order are the subexpressions evaluated?

   1. min(max(3, 4), abs(-5))
   2. abs(min(4, 6, max(2, 8)))
   3. round(max(5.572, 3.258), abs(-2))

3. Following the function design recipe, define a function that has one parameter, a number, and returns that number tripled.

4. Following the function design recipe, define a function that has two parameters, both of which are numbers, and returns the absolute value of the difference of the two. Hint: Call built-in function abs.

5. Following the function design recipe, define a function that has one parameter, a distance in kilometers, and returns the distance in miles. (There are 1.6 kilometers per mile.)

6. Following the function design recipe, define a function that has three parameters, grades between 0 and 100 inclusive, and returns the average of those grades.

7. Following the function design recipe, define a function that has four parameters, all of them grades between 0 and 100 inclusive, and returns the average of the best 3 of those grades. Hint: Call the function that you defined in the previous exercise.

8. Complete the examples in the docstring and then write the body of the following function:

   ​	​def​ weeks_elapsed(day1, day2):
   ​	​""" (int, int) -> int​
   ​
   ​	​ day1 and day2 are days in the same year. Return the number of full weeks​
   ​	​ that have elapsed between the two days.​
   ​
   ​	​ >>> weeks_elapsed(3, 20)​
   ​	​ 2​
   ​	​ >>> weeks_elapsed(20, 3)​
   ​	​ 2​
   ​	​ >>> weeks_elapsed(8, 5)​
   ​
   ​	​ >>> weeks_elapsed(40, 61)​
   ​
   ​	​ """​

9. Consider this code:

   ​	​def​ square(num):
   ​	​""" (number) -> number​
   ​
   ​	​ Return the square of num.​
   ​
   ​	​ >>> square(3)​
   ​	​ 9​
   ​	​ """​

   In the following table, fill in the Example column by writing square, num, square(3), and 3 next to the appropriate description.

   Description	Example
   Parameter
   Argument
   Function name
   Function call

10. Write the body of the square function from the previous exercise.