Exercises

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

1. Variable kingdoms refers to the list [’Bacteria’, ’Protozoa’, ’Chromista’, ’Plantae’, ’Fungi’, ’Animalia’]. Using kingdoms and either slicing or indexing with positive indices, write expressions that produce the following:

   1. The first item of kingdoms
   2. The last item of kingdoms
   3. The list [’Bacteria’, ’Protozoa’, ’Chromista’]
   4. The list [’Chromista’, ’Plantae’, ’Fungi’]
   5. The list [’Fungi’, ’Animalia’]
   6. The empty list

2. Repeat the previous exercise using negative indices.

3. Variable appointments refers to the list [’9:00’, ’10:30’, ’14:00’, ’15:00’, ’15:30’]. An appointment is scheduled for 16:30, so ’16:30’ needs to be added to the list.

   1. Using list method append, add ’16:30’ to the end of the list that appointments refers to.

   2. Instead of using append, use the + operator to add ’16:30’ to the end of the list that appointments refers to.

   3. You used two approaches to add ’16:30’ to the list. Which approach modified the list and which approach created a new list?

4. Variable ids refers to the list [4353, 2314, 2956, 3382, 9362, 3900]. Using list methods, do the following:

   1. Remove 3382 from the list.
   2. Get the index of 9362.
   3. Insert 4499 in the list after 9362.
   4. Extend the list by adding [5566, 1830] to it.
   5. Reverse the list.
   6. Sort the list.

5. In this exercise, you’ll create a list and then answer questions about that list.

   1. Assign a list that contains the atomic numbers of the six alkaline earth metals—beryllium (4), magnesium (12), calcium (20), strontium (38), barium (56), and radium (88)—to a variable called alkaline_earth_metals.
   2. Which index contains radium’s atomic number? Write the answer in two ways, one using a positive index and one using a negative index.
   3. Which function tells you how many items there are in alkaline_earth_metals?
   4. Write code that returns the highest atomic number in alkaline_earth_metals. (Hint: Use one of the functions from Table 10, ​List Functions​.)

6. In this exercise, you’ll create a list and then answer questions about that list.

   1. Create a list of temperatures in degrees Celsius with the values 25.2, 16.8, 31.4, 23.9, 28, 22.5, and 19.6, and assign it to a variable called temps.
   2. Using one of the list methods, sort temps in ascending order.
   3. Using slicing, create two new lists, cool_temps and warm_temps, which contain the temperatures below and above 20 degrees Celsius, respectively.
   4. Using list arithmetic, recombine cool_temps and warm_temps into a new list called temps_in_celsius.

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

   ​	​def​ same_first_last(L: list) -> bool:
   ​	​"""Precondition: len(L) >= 2​
   ​
   ​	​ Return True if and only if first item of the list is the same as the​
   ​	​ last.​
   ​
   ​	​ >>> same_first_last([3, 4, 2, 8, 3])​
   ​	​ True​
   ​	​ >>> same_first_last(['apple', 'banana', 'pear'])​
   ​
   ​	​ >>> same_first_last([4.0, 4.5])​
   ​
   ​	​ """​

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

   ​	​def​ is_longer(L1: list, L2: list) -> bool:
   ​	​"""Return True if and only if the length of L1 is longer than the length​
   ​	​ of L2.​
   ​
   ​	​ >>> is_longer([1, 2, 3], [4, 5])​
   ​	​ True​
   ​	​ >>> is_longer(['abcdef'], ['ab', 'cd', 'ef'])​
   ​
   ​	​ >>> is_longer(['a', 'b', 'c'], [1, 2, 3]​
   ​
   ​	​ """​

9. Draw a memory model showing the effect of the following statements:

   ​	values = [0, 1, 2]
   ​	values[1] = values

10. Variable units refers to the nested list [[’km’, ’miles’, ’league’], [’kg’, ’pound’, ’stone’]]. Using units and either slicing or indexing with positive indices, write expressions that produce the following:

    1. The first item of units (the first inner list)
    2. The last item of units (the last inner list)
    3. The string ’km’
    4. The string ’kg’
    5. The list [’miles’, ’league’]
    6. The list [’kg’, ’pound’]

11. Repeat the previous exercise using negative indices.