Py4e: Chapter 9

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

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

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

False

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

How are Python dictionaries different from Python lists?

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

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

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()