Quiz 3- Chapter’s 9-11

Question 1

define a dictionary

Answer 1

an object that stores a collection of data.

elements are ordered, changeable and DO NOT allow duplicates

KEY VALUE PAIRS are elements

Question 2

Is a key immutable or mutable

Answer 2

Key’s are immutable

Question 3

are dictionaries mutable?

Answer 3

yes

Question 4

How do you retrieve a specific value from a dictionary?

Answer 4

You use the key associated with it

Question 5

Dictionaries are ordered. What does that mean

Answer 5

that the items have a defined order and that order will not change. Unordered means that the items do not have a defined order and you cannot refer to an item by using an index

Question 6

dictionary format:

Answer 6

{key1:val1,key2:val2,key3:val3}

Question 7

What will this do?

variable = {}

What built-in function will accomplish the same thing?

Answer 7

It will create an empty dictionary.

dict() will accomplish the same thing

Question 8

what will this do?

cars = {‘’brand’’:’’Ford’’,’’model’’:’’Mustang’’,’’year’’:1964}

print(cars)

Answer 8

it will display the dictionary.

Question 9

What will this do?

dictionary[key] = value

Answer 9

Add the new element to the dictionary. If the key already exists it will change the value associated with it

Question 10

dictionary[key]

What will this do?

Answer 10

retrieve the value from the dictionary. If key is in the dictionary, otherwise KeyError exception is raised.

Question 11

What’s a way to test and see if a key is in a dictionary?

Answer 11

using the in and not in operators.

if ‘’model’’ in cars:
print(‘’Yes, ‘model’ is a key’’)

Question 12

cars = {‘’brand’’:’’Ford’’,’’model’’:’’Mustang’’,’’year’’:1964}

x = cars.values()
print(x)

What is the output?

Answer 12

dict_values([‘Ford’,’Mustang’,1964])

Question 13

How do you retrieve elements from a dictionary?

cars = {‘’brand’’:’’Ford’’,’’model’’:’’Mustang’’,’’year’’:1964}

Answer 13

x = cars.items()
print(x)

it will display the key value pair

Question 14

del dictionary[key]

Will do what?

Answer 14

delete the key-value pair in the dictionary. If key is not in dictionary, KeyError exception is raised.

Question 15

What does the len function do?

Answer 15

Used to obtain the number of elements in a dictionary.

Key must be immutable but values can be any type of object.

One dictionary can include keys of several different immutable tuples.

Values stored in a single dictionary can be of different types

Question 16

clear method

Answer 16

deletes all the elements in a dictionary, leaving it empty

format: dictionary.clear()

Question 17

What does the get method do?

Answer 17

gets a value associated with a specified key from dictionary

format: dictionary.get(key,default)

default is returned if key is not found

alternative to [] operator

CANNOT RAISE KEYERROR EXCEPTION

Question 18

items method:

Answer 18

returns all the dictionaries keys and values

format: dictionary.items()

returned as dictionary view

each element in dictionary view is a tuple which contains a key and its value
USE A FOR LOOP to iterate over the tuples in the sequence

Question 19

keys method:

Answer 19

returns all the dictionary keys as a sequence

format: dictionary.keys()

Question 20

pop method:

Answer 20

returns value with specified key and removes that key-value pair from the dictionary

format: dictionary.pop(key,default)

default is returned if key is not found

Question 21

popitem method:

Answer 21

returns, as a tuple, the key value pair that was last added to the dictionary. The method also removes the pair from the dictionary.

format: dictionary.popitem()

KEY VALUE PAIR RETURNED AS TUPLE

Question 22

values method:

Answer 22

returns all the dictionary values as a sequence

format: dictionary.values()

use for loop to iterate over values

Question 23

dictionary comprehension:

Answer 23

an expression that reads a sequence of input elements and uses those input elements to produce a dictionary

Question 24

what is this an example of:

squares = {item:item**2 for item in numbers}

Answer 24

dictionary comprehension.

The results expressions is item:item**2

the iteration expression is for item in numbers

Question 25

names = { ‘Jeremy’, ‘Kate’,’Peg’} variable = {item:len(item) for item in names} variable What will the output produce?

Answer 25

It will display the length of each name for each item in the list {‘Jeremy’:6,’Kate’,:4,’Peg’:3}

Question 26

dict1 = {‘A’:1,’B ‘:2,’C’:3} dict2 = {k:v for k,v in dict1.items()} dict 2 What will this do?

Answer 26

produce a copy of the first dictionary {‘A’:1,’B ‘:2,’C’:3}

Question 27

Can you use an if clause in dictionary comprehension statements?

Answer 27

Yes, to select only certain elements of the input sequence.

Question 28

set:

Answer 28

an object that stores a collection of data in same ways as mathematical set -all items must be unique (no duplicates) -set is unordered - elements can be of different data types

Question 29

set function:

Answer 29

used to create a set for empty set: call set() for non empty set: call set(argument) where argument is an object that contains iterable elements. (ex: list, string, tuple, can all be argument) but if the argument is a string each character becomes a set element. For set of strings, pass them to the function as a list. if argument contains duplicates, only one of the duplicates will appear in the list

Question 30

len function for a set:

Answer 30

returns the number of elements in a set

Question 31

Are sets mutable or immutable?

Answer 31

mutable

Question 32

add method (for a set)

Answer 32

adds an element to a set

Question 33

update method (for a set)

Answer 33

updates a group of elements to a set. (arguments must be a sequence containing iterable elements and each of the elements is added to the set)

Question 34

remove and discard method both do what? (for a set)

Answer 34

remove the specified item from the set. The item that should be removed is passed to both methods as an argument. Behave differently when THE SPECIFIED ITEM IS NOT FOUND IN THE SET

Question 35

what error does remove method raise when specified item is not found in a set?

Answer 35

KeyError exception

Question 36

What error does discard method raise when the specified item is not found in the set?

Answer 36

IT DOES NOT RAISE AN EXCEPTION

Question 37

clear method (for a set):

Answer 37

clears all the elements of the set.

Question 38

What kind of loop can be used to iterate over each element in a set? how many times does the loop iterate for each item in the set?

Answer 38

A for loop. Once. format: for item in set:

Question 39

What operator can test whether a value is in set or not?

Answer 39

in, not in

Question 40

Union of 2 sets:

Answer 40

a set that contains all the elements of both sets

Question 41

How do you find the union of 2 sets:

Answer 41

use the union methodL format: set1.union(set2) or use the | operator format: set1 | set2 BOTH RETURN A NEW SET WHICH CONTAINS THE UNION OF BOTH SETS

Question 42

Intersection of 2 sets:

Answer 42

a set that contains only the elements found in both sets

Question 43

How do you find the intersection of 2 sets?

Answer 43

use the intersection method: format: set1.intersection(set2) or use the & operator format: set1 & set2 BOTH TECHNIQUES RETURN A NEW SET WHICH CONTAINS THE INTERSECTION OF BOTH SETS

Question 44

Difference of 2 sets:

Answer 44

a set that contains elements that appear in the first set but do not appear in the second set

Question 45

How do you find the difference of 2 sets:

Answer 45

Use the difference method: Format: set1.difference(set2) or Use the - operator: format: set1 - set2

Question 46

Symmetric difference of 2 sets:

Answer 46

a set that contains the elements that are not shared by the 2 sets

Question 47

How to find the symmetric difference of 2 sets:

Answer 47

use the symmetric_difference method: format: set1.symmetric_difference(set2) or use the ^ operator: format: set1 ^ set2

Question 48

When is set A a subset of set B?

Answer 48

if all the elements in set A are included in set B

Question 49

To determine whether set A is a subset of set B:

Answer 49

use the issubset method: format: setA.issubset(setB) or use the <= operator: format: setA <= setB

Question 50

set A is a superset of set B if

Answer 50

it contains all the elements of set B

Question 51

To determine whether set A is a superset of set B:

Answer 51

use the issuperset method: format: setA.issuperset(setB) use the >= operator format: setA >= setB

Question 52

set comprehension:

Answer 52

a concise expression that creates a new set by iterating over the elements of a sequence. Set comprehensions are written like comprehensions except they are enclosed in curly brackets {}

Question 53

serializing objects:

Answer 53

convert the object to a stream of bytes that can easily be stored in a file

Question 54

pickling:

Answer 54

serializing an object

Question 55

Procedural programming

Answer 55

writing programs made of functions that perform specific tasks. data items commonly passed from one procedure to the next

Question 56

Is python an object-oriented programming language?

Answer 56

Yes, almost everything in python is an object

Question 57

object-oriented programming

Answer 57

focused on creating objects

Question 58

object:

Answer 58

entity that contains data and procedures

Question 59

data is known as

Answer 59

data attributes

Question 60

procedures are known as

Answer 60

methods

Question 61

What do methods do?

Answer 61

perform operations on the data attributes

Question 62

encapsulation:

Answer 62

combining data and code into a single object

Question 63

data hiding (object?)

Answer 63

data attributes are hidden from code outside the object outside code does NOt need to know the internal structure of the object, PROTECTS AGAINST ACCIDENTAL CORRUPTION

Question 64

object reusability:

Answer 64

the same object can be used in different programs

Question 65

data attributes:

Answer 65

define the state of an object: ex: clack would have second, minute, and hour attributes

Question 66

public methods:

Answer 66

allow external code to manipulate the object

Question 67

private methods:

Answer 67

used for object’s inner workings

Question 68

class:

Answer 68

code that specifies the data attributes and methods of a particular type of object (blueprint, cookie cutter)

Question 69

instance

Answer 69

an object created from a class there can be many instances of 1 class class: set of instructions for how to make an instance

Question 70

class Cookie(): does what

Answer 70

creates a class named Cookie

Question 71

Class definitions:

Answer 71

set of statements that define a class’s methods and data attributes format: class Class_Name: class names often begin with uppercase letter

Question 72

self parameter:

Answer 72

required in every method in the class_references the specific object that the method is working on

Question 73

initializer method:

Answer 73

automatically executed when an instance of the class is created: format: def__init__(self): usually first method in class definition DOES NOT HAVE TO BE CALLED SELF

Question 74

What will this do? car = class_name()

Answer 74

create an instance of a class

Question 75

to call a class what notation do you use

Answer 75

dot notation: my_instance.method()

Question 76

what does this do self.__current_minute ?

Answer 76

makes sure that the object’s data attributes are private by placing two underscores in front of the attribute

Question 77

accessing attributes is done through?

Answer 77

dot notation ex: self.name

Question 78

you call method using

Answer 78

dot notation ex: my_cat.play()

Question 79

The self parameter is a reference to

Answer 79

the current instance of the class

Question 80

self (in classes) is used to

Answer 80

access variables that belongs to the class. the parameter does not have to be named self but it must be the first parameter of any function in teh class

Question 81

Pure or Accessor methods:

Answer 81

a function which creates an object, initializes its attributes, and returns a reference to the new object ex: get_model is an accessor method

Question 82

Modifiers or Mutator methods

Answer 82

a function which modifies the objects it gets as parameters where the changes are visible to the caller ex: set_model

Question 83

Mutator methods are sometimes called____ and accessor methods are sometimes called ____

Answer 83

Mutator: “setters” accessor: “getters”

Question 84

modifier:

Answer 84

a function that modifies the object it gets as parameter. Changes are visible to the caller (function)

Question 85

Object properties can be modified and deleted?

Answer 85

yes: p1 = Person(“john”,36) p1.age = 40 print(p1.age) 40 del p1.age print(p1.age). gives you an AttributeError (object person has no attribute age)

Question 86

Object oriented programming languages usually require what kind of functions?

Answer 86

pure functions: programs are faster and less error-prone

Question 87

Can class definitions be empty?

Answer 87

No, but you can use the pass method to avoid the error message (same as functions)

Question 88

Instance dictionary :

Answer 88

an interval value used by classes

Question 89

object’s state:

Answer 89

the values of the object’s attributes at any given moment

Question 90

__str__(self) helps you do what

Answer 90

control what information gets printed for a class.

Question 91

UML stands for what

Answer 91

unified modeling language

Question 92

UML definition:

Answer 92

standard diagram for graphically depicting object-oriented systems top: name of class middle: attributes bottom: methods

Question 93

Inheritance:

Answer 93

when one class inherits from another. It takes on the attributes and methods of the 1st class

Question 94

parent class:

Answer 94

the original class

Question 95

child class:

Answer 95

the new class which inherits any or all of the attributes and methods of its parent class AND is also free to define new methods and attributes

Question 96

“Is a” relationship:

Answer 96

exists when 1 object is a specialized version of another object -the specialized object has all the characteristics of the general object plus unique characteristics ex: rectangle is a shape, daisy is a flower

Question 97

Inheritance is used to create what kind of relationship between classes

Answer 97

“is a” relationship

Question 98

Superclass (base or parent class)

Answer 98

a general class

Question 99

subclass( derived or child class)

Answer 99

a specialized class that is an extended version of the superclass but can have its own new attributes and methods added.

Question 100

Using __init__ for child will initialize any attributes that were defined in the parent __int__() which makes:

Answer 100

all or selected attributes available in the child class

Question 101

polymorphism:

Answer 101

an objects ability to take different forms

Question 102

what are some essential ingredients of polymorphic behavior?

Answer 102

- ability to define a method in a superclass and override it in a subclass (subclass defines method with same name) - ability to call the correct version of overridden method depending on the type of object that called for it

Question 103

does polymorphism provide great flexibility when designing programs?

Answer 103

yes

Question 104

AttributeError exception:

Answer 104

raised when a method receives an object which is not an instance of the right class

Question 105

isinstance function

Answer 105

determines whether an object is an instance of a class format: isinstance(object, class)

Question 106

__init__ is short for, and does what

Answer 106

“initialization”, and it is a special method that gets invoked when an object is instantiated

Question 107

__str__() does what

Answer 107

it is a special method that is supposed to return a string representation of an object when you print an object python invokes the str method implicitly. The __str__ method is useful for debugging

Question 108

polymorphism:

Answer 108

functions that work with several types and encourages code reuse (AKA the intent of object oriented programming CODE REUSE)