Week 4 Exercises

Lists, List Comprehensions

Examples and Exercises modeled after: http://www.upriss.org.uk/python/session5.html

zoo = ["giraffe", "crow"]               # define a list
zoo[0]                                  # a single element
zoo[0] = "zebra"                        # change an element
zoo.append("marmot")                    # add element at end of list
zoo = ["cat"] + zoo                     # add element at beginning
type(raw_input("Type a string: "))      # returns str
type(    input("Type a number: "))      # returns int or float
[x for x in zoo if len(x) > 4]          # list comprehension
zoo2 = zoo[:]                           # create a list copy
zoo.pop()                               # delete last element
del zoo[0]                              # delete element by index
zoo.remove('crow')                      # delete element by value
"abc"[::-1]                             # reverse a string: "cba"
                                        # Unspecified range takes all; step value of -1 reverses.

1. Create a list that contains "Apples", "Pears", "Oranges" and "Peaches". Display the list. Ask the user for another fruit and add it to the end of the list. Display the list. Ask the user for a number and display the number back to the user and the fruit corresponding to that number (on a 1-is-first basis). Add another fruit to the beginning of the list using "+" and display the list. Display all the fruits that begin with "P", first using a for loop and then using a list comprehension.

2. Using the list above: Display the list. Remove the last fruit from the list. Display the list. Ask the user for a fruit to delete and find it and delete it. (Bonus: Multiply the list times two. Keep asking until a match is found. Once found, delete all occurrences.)

3. Using the list in item 1: Ask the user for input displaying a line like "Do you like apples?" for each fruit in the list (making the fruit all lowercase). For each "no", delete that fruit from the list. Display the list.

4. Using the list in item 1: Make a copy of the list and reverse the letters in each fruit in the copy. Delete the last item of the original list. Display the original list and the copy.