Python Dictionaries

Which of the following are true of Python dictionaries:

• Dictionaries can be nested to any depth.

• Dictionaries are accessed by key.

• All the keys in a dictionary must be of the same type.

• Dictionaries are mutable.

• A dictionary can contain any object type except another dictionary.

Which of the following is not a valid way to define this dictionary in Python:

• d = dict([

  ('foo', 100),

  ('bar', 200),

  ('baz', 300)

  ])

• d = {}

  d['foo'] = 100

  d['bar'] = 200

  d['baz'] = 300

• d = dict(foo=100, bar=200, baz=300)

• d = {'foo': 100, 'bar': 200, 'baz': 300}

• d = { ('foo', 100), ('bar', 200), ('baz', 300) }

Consider this dictionary:

d = {'foo': 100, 'bar': 200, 'baz': 300}

What is the result of this statement:

d['bar':'baz']

• It raises an exception

• (200, 300)

• 200 300

• [200, 300]

Suppose x is defined as follows:

x = [

'a',

'b',

{

'foo': 1,

'bar':

{

'x' : 10,

'y' : 20,

'z' : 30

},

'baz': 3

},

'c',

'd'

]

What is the expression involving x that accesses the value 30?

• x[2]["bar"]["z"]

• x[2]["bar"]

• x["bar"]["z"]

• x[2]["bar"]["z"][3]

Which of the following could be a valid dictionary key:

• (3+2j)

• ('foo', 'bar')

• dict(foo=1, bar=2)

• 'foo'

• ['foo', 'bar']

You have the following dictionary definition:

d = {'foo': 100, 'bar': 200, 'baz': 300}

What method call will delete the entry whose value is 200?

• delete d('bar')

• d.pop("bar")

• d.remove("bar")

• None of the above

Suppose you have a dictionary d1. Which of the following effectively creates a variable d2 which contains a copy of d1:

• d2 = dict(d1.items())

• d2 = dict(d1.keys())

• d2 = {}

  d2.update(d1)

• d2 = dict(d1.values())

• d2 = dict(d1)

What would be the output of the following code snippet?

a_dict = {'color': 'blue', 'fruit': 'apple', 'pet': 'dog'}

for key in a_dict:

print(key)

• 'blue'

  'apple'

  'dog'

• color

  fruit

  pet

• blue

  apple

  dog

• 'color'

  'fruit'

  'pet'

What would be the output of the following code snippet?

a_dict = {'color': 'blue', 'fruit': 'apple', 'pet': 'dog'}

d_items = a_dict.items()

print(d_items)

• ('color', 'blue'), ('fruit', 'apple'), ('pet', 'dog')

• dict_items([('color'), ('fruit'), ('pet')])

• [('color', 'blue'), ('fruit', 'apple'), ('pet', 'dog')]

• dict_items([('color', 'blue'), ('fruit', 'apple'), ('pet', 'dog')])

Consider the following statement:

If you just need to work with the keys of a dictionary, then you can use .keys(), which is a method that returns a new view object containing the dictionary’s keys.

Is this statement True or False?

• False

• True