M03 - Dictionaries

Question 1

Dictionary definition + contents

Answer 1

• Object that stores a collection of data

- Has a key and a value or key-value pairs (think dictionary where there’s Word-Definition)

Question 2

Key-Value Pairs example with 2 keys/how a dictionary prints out

Answer 2

{‘key1’ : value1 , ‘key2’ : value2 , etc.}

Question 3

2 Important Rules for Dictionaries

Answer 3

1. Keys must be immutable objects, like integers, floating-point decimals, or strings. Keys cannot be lists or any other time of mutable object
2. Values in a dictionary can be objects of any type: integers, floating-point decimals, strings, Boolean values, datetime values, and lists

Question 4

Initialize/Create an empty dictionary options

Answer 4

dict_variable = { }

dict_variable = dict( )

Question 5

Standard format for creating a key in a dictionary and syntax example

Answer 5

-Place the key between single or double quotes and inside brackets [ ]

dict_variable[“key1”] = value1

Question 6

Length of a dictionary

Answer 6

len(dict_variable)

Question 7

items( ) method on dictionary and when it cannot be used

Answer 7

• Will return a list of tuples where the first element in each tuple is the key of the dictionary and the second element in each tuple is the value corresponding to that key
• Cannot use list indexing with the items( ) method

Question 8

items( ) Syntax + output example

Answer 8

dict_variable.items( )

Output:
dict_variable( [ (‘key1’ , value1) , (‘key2’ , value2) , …] )

Question 9

View Object - what it is and what it gives us

Answer 9

• Is the information inside the dict_variable( [ ] ) in the output
• Gives us a snapshot of what is in the dictionary (provides each key and respective value)

Question 10

Get all Keys from Dictionary method and syntax

Answer 10

keys( )

dict_variable.keys( )

Question 11

keys( ) method returns

Answer 11

Will return a view object that contains the keys of the dictionary as a list

dict_variable( [ ‘Key1’, ‘Key2’ , ‘Key3’ , …. ] )

Question 12

Get all Values from Dictionary method and syntax

Answer 12

values( )

dict_varible.values( )

Question 13

values( ) method returns

Answer 13

-Returns a view object that contains the values of the dictionary as a list

dict_variable( [‘value1’ , ‘value2’ , ‘value3’ …. ] )

Question 14

2 ways to get a specific VALUE from a dictionary and a note about syntax

Answer 14

get( )

dict_variable[‘keyname’]

*both require the key to be in single or double quotes

Question 15

get( ) syntax

Answer 15

dict_variable.get(‘keyname’)

Question 16

Lists of Dictionaries

Answer 16

-Dictionaries can have the same keys associated with different values formatted as:
[ {‘key1’ : value1 , ‘key2’ : value2} , {‘key1’ : value3, ‘key2’ : value4} , ….]

-Each dictionary is wrapped in { }

Question 17

append( ) + dictionary w/ 2 keys syntax

Answer 17

dict_variable.append( {‘key1’ : value1 , ‘key2’ : value2})

Question 18

CSV Format and List of Dictionaries

Answer 18

Think of Keys as column headers and values as the respective row data

Question 19

List Methods (on dictionaries) can be used to (4x):

Answer 19

1. Get the length of the dictionary - len(dict_variable)
2. Use indexing and slicing to get one or more dictionaries - dict_variable[index]
3. Use the append( ), insert( ), and remove( ) methods to add and remove one or more dictionaries
4. Change a value for one of the keys in the list of dictionaries