soln2_2.md

Exercise 2.2 - Solution

There is no official solution for this exercise--you need rely on your current Python knowledge. However, there are a few tips that can help.

• For problems where you need to determine uniqueness, use a set. Sets aren't allowed to have duplicates.

• If you need to tabulate data, consider using a dictionary that maps keys to a numeric count. For example, to count rides on each bus route, you could make a dictionary that maps the route name to the total ride count for that route. A Counter object from collections is perfect for this task.

• If you need to keep data in order or sort data, store it in a list.

• You can make Python data structures out of almost anything. For example, dictionaries of sets, nested dictionaries, etc. You might need to do this to answer questions 3 and 4.

Even though no code is provided, here are some answers to the questions so that you can check your work:

1. How many bus routes exist in Chicago? (Answer: 181)

2. How many people rode the number 22 bus on February 2, 2011? (Answer: 5055)

3. What is the total number of rides taken on each bus route? (Answer: for the top three routes, [('79', 133796763), ('9', 117923787), ('49', 95915008)])

4. What five bus routes had the greatest ten-year increase in ridership from 2001 to 2011? (Answer: [('15', 2732209), ('147', 2107910), ('66', 1612958), ('12', 1612067), ('14', 1351308)])

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