Ch 6.

Question 1

What is a dictionary in python?

Answer 1

A collection of key-value pairs, where each key is connected to a value, and you can use a key to access the value associated with that key.
Note: value can be any of the data types

Question 2

Generic dictionary looks like?

Answer 2

dictionary_name = { “a”: “one”, “b” : “two}
where a and b are keys
and one and two are their associated values

Question 3

How do you print the associated value of a key?

Answer 3

print(dictionary_name[key])

where the value should be printed

Question 4

How do you add new key-value pairs to a dictionary?

Answer 4

dictionary_name[“key”] = “value”

Question 5

When do you typically start off with an empty dictionary?

Answer 5

When storing user-supplied data or when you write code that generates a large number of key-value pairs automatically.

Question 6

How do you modify values in a dictionary?

Answer 6

Same as adding new key values but of course you are just changing the value

Question 7

How do you remove a key value pair?

Answer 7

using the del statement: del dictionary_name[“a”]

Question 8

What is the get() method used for?

Answer 8

To set a default value that will be returned if the requested key doesn’t exist.

Question 9

How is get() used?

Answer 9

value = foo.get(key)

Value will either be the “value” or None

Question 10

What are the different ways to loop through a dictionary?

Answer 10

Can loop through all of the dictionary’s key value pairs, through its keys, or through it’s values.

Question 11

What does the method items() do?

Answer 11

Returns a list of key value pairs

Question 12

How do you loop through all key value pairs?

Answer 12

for key, value in dictionary_name.items():

Question 13

What is the keys() method useful for?

Answer 13

To iterate the keys of the dictionary

Question 14

How do you loop through all the keys in a dictionary?

Answer 14

for key_name in dictionary_name.keys()

Question 15

What else can you do with the keys() method?

Answer 15

Check if a key is in a dictionary

Question 16

How do you check if a key is in a dictionary?

Answer 16

if key_name in dictionary_name.keys()

Question 17

How do you loop though a dictionary’s keys in alphabetical order?

Answer 17

for key_name in sorted(dictionary_name.keys()):

Question 18

What is the values() method used for?

Answer 18

Returning a list of values w/o any keys.

Question 19

How do you loop through all values in a dictionary?

Answer 19

for value_name in dictionary_name.values():

Question 20

What is a set?

Answer 20

A collection in which each item must be unique.

Question 21

What happens when you wrap set() around a list that contains duplicate items?

Answer 21

Python identifies the unique items in the list and builds a set from those items.

Question 22

A set wraps it’s items in?

Answer 22

Braces

Question 23

What is nesting?

Answer 23

Storing multiple dictionaries in a list, or a list of items as a value in a dictionary. You can nest dictionaries inside a list, a list of items inside a dictionary, or even a dictionary inside another dictionary.

Question 24

How do you use a list in a dictionary?

Answer 24

The value in the dictionary is actually a list. You can nest a list inside a dcitionary any time you want more than one value to be assocaited with a single key in a dictionary.

Question 25

Look up is faster in a list or a set/dict?

Answer 25

Set/dict is faster

Question 26

How do you use items()?

Answer 26

for key, value in dictionary_name.items()

Question 27

Whats the difference between keys, values and items?

Answer 27

.keys() returns keys
.values() returns values
.items() returns a tuple (key, value)

Question 28

Does order matter in a dictionary or set?

Answer 28

Nope