Chapter 9 Quiz

10?試題

1.?

How are Python dictionaries different from Python lists?

Python lists maintain order and dictionaries do not maintain order

Python lists can store strings and dictionaries can only store words

Python dictionaries are a collection and lists are not a collection

Python lists store multiple values and dictionaries store a single value

2.?

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

Lambdas

Sequences

Associative arrays

Closures

3.?

What would the following Python code print out?

stuff = dict() print stuff['candy']

0

-1

The program would fail with a traceback

candy

4.?

What would the following Python code print out?

stuff = dict() print stuff.get('candy',-1)

0

-1

'candy'

The program would fail with a traceback

5.?

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

False

True

6.?

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

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

Splitting a line of input into words using a space as a delimiter

Computing an average of a set of numbers

Sorting a list of names into alphabetical order

7.?

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] = (key in counts) + 1

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

counts[key] = (counts[key] * 1) + 1

counts[key] = key + 1

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

8.?

In the following Python, what does the?for?loop iterate through?

x = dict() ... for y in x :...

It loops through all of the dictionaries in the program

It loops through the integers in the range from zero through the length of the dictionary

It loops through the keys in the dictionary

It loops through the values in the dictionary

9.?

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

items()

keys()

each()

all()

values()

10.?

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

The value to retrieve

To provide a default value if the key is not found

The key to retrieve

An alternate key to use if the first key cannot be found

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