Py4e: Chapter 9

How are Python dictionaries different from Python lists?

Python lists are indexed using integers and dictionaries can use strings as indexes

What would the following Python code print out? stuff = dict() print(stuff.get('candy',-1))

-1 not The program would fail with a traceback

What is a term commonly used to describe the Python dictionary feature in other programming languages?

Associative arrays

What would the following Python code print out? stuff = dict() print(stuff['candy'])

The program would fail with a traceback notcandy

Which of the following lines of Python is equivalent to the following sequence of statements assuming that counts is a dictionary? if key in counts: counts[key] = counts[key] + 1 else: counts[key] = 1

counts[key] = counts.get(key,0) + 1

Which method in a dictionary object gives you a list of the values in the dictionary?

values()

What is a common use of Python dictionaries in a program?

Building a histogram counting the occurrences of various strings in a file

In the following Python, what does the for loop iterate through? x = dict() ... for y in x : ...

It loops through the keys in the dictionary

What is the purpose of the second parameter of the get() method for Python dictionaries?

To provide a default value if the key is not found

(T/F) When you add items to a dictionary they remain in the order in which you added them.

False