Chapter 14-Tuples, Sets, Dictionaries

Question 1

What does a tuple do?

Answer 1

Tuples store a fixed list of elements

Question 2

What does a dictionary do?

Answer 2

A dictionary stores key/value pairs and for accessing elements quickly using the keys.

Question 3

What are tuples?

Answer 3

Tuples are like lists, but their elements are fixed;that is, once a tuple is created, you cannot add new elements, delete elements, replace elements or reorder elements in the tuple.

Just like lists, tuples are sequences so you may use functions like len, min, max, sum, in, not in. A for loop can be used to traverse all elements in a tuple and the tuple elements can be accessed using an index operator.

Question 4

How do you create a tuple?

Answer 4

By enclosing a tuple’s elements inside a pair of parentheses. The elements are separated by commas.

Question 5

Make a basic tuple…NAOW!!

Answer 5

looks like anything:

t1=( )
t2=(1,3,5)
t3=tuple([2 * x for x in range(1 , 5)])

You can also create a tuple from a string. Each character in the string becomes an element in the tuple:
t4=tuple(‘abac’) #t4 is [’ a ‘, ‘ b ‘, ‘ a ‘, ‘ c ‘]

Question 6

What are sets?

Answer 6

Sets are like lists in that you use them for storing a collection of elements. Unlike lists however, the elements in a set are nonduplicates and are not placed in any particular order.

Question 7

How do you create a set?

Answer 7

You create a set of elements by enclosing the elements inside a pair of curly braces. The elements are separated by commas.

You can create an empty set or from a list or a tuple.

Question 8

Create an empty set, a set from a list and a set from a tuple.

Also, create a set from a list, what would the output look like?

Answer 8

s1=set( )
s2= {1,3,5} #set with three elements
s3=set( [ 1,3,5] ) #set from a tuple
s4=set( [x*2 for x in range(1,10) ] )

s5=set(‘aba’)
output–> {‘a’, ‘b’, ‘a’}

Question 9

How do you create a set from a list or tuple?

Answer 9

list(set)

tuple(set)

Question 10

What is the output of this set? s1= {‘abac’}

Answer 10

{‘a’, ‘b’, ‘a’}

Remember that sets do not store duplicates.

Question 11

Can a set contain different elements like strings and numbers?

Answer 11

Yes they can: s2= {1,2,3, ‘one’, ‘two’, ‘three’}

Question 12

What are some ways you can manipulate a set?

Answer 12

add(e)
ex. s2= {1,2,4}
s1.add(6)
>>s1
output--> {1,2,4,6}
remove(e)
#the above add and remove elements from a set

len ,min,max, sum

you can use a for loop to transverse all elements in a set

in, not in (used to determine whether or not an element is in a set)

Question 13

s1= {1,2,4}
s2={1,4,5,2,6}

How do you check if s2 is a subset of s1? What is a subset?

Answer 13

s1= {1,2,4}
s2={1,4,5,2,6}
–>s1.issubset(s2)
True

A set is a subset of the other if every element, say in s1 is in s2. Which in this case is true. (The bigger set has some elements that match with the smaller one)

Question 14

s1= {1,2,4}
s2={1,4,5,2,6}
How do you check s1 us a super set of s2? What is a superset?

Answer 14

s1= {1,2,4}
s2={1,4,5,2,6}
s2.issuperset(s1)
True

A super set is if a set like s1 is a superset of set s2; if every element in s2 is also in s1. (The smaller set is in the bigger set)

(ignore the super and subset, it’s being confusing on page 480) ( I am skipping sets, they have that subset shit in it)

Question 15

What is a dictionary(more detailed explanation)?

Answer 15

A dictionary is a container object that stores a collection of key/value pairs. It enables fast retrieval, deletion and updating of the value by using the key.

Question 16

How do you add, modify and retrieve values in a dictionary?

Answer 16

To add, you use the syntax: dictionaryName[key]=value
ex. students[“234-56-9010”]= “Susan”

If the key is already in the dictionary, the preceding statement replaces the value for the key.

To retrieve a value, write: dictionaryName[key]. The value of the key will be returned.

Question 17

How do you delete an item in a dictionary?

Answer 17

del dictionaryName[key]

ex. del students[“234-56-9010”]

Question 18

How do you find the number of items in a dictionary?

Answer 18

with the len function:

students={“12-34-5”=”John”, “98-76-5”=”Peter”}
»>len(students)
2

Question 19

How do you test whether a key is in a dictionary or not?

Answer 19

use the in, not in functions.

Question 20

What is the python class for dictionary?

Answer 20

dict( )

Question 21

Here are the list of methods that can be invoked from a dictionary:
keys( ): tuple
values( ): tuple
items( ): tuple
clear( ): None
get(key): value
pop(key): value
popitem( ): tuple

What do each of them do?

Answer 21

keys( )-returns sequences of keys

values( )-return sequences of values

items( )- Returns sequences of tuples. Each tuple is a (key,value) for an item.

clear( )- Deletes all entries

get(key)- Returns the value for the key. The get(key) method is similar to dictionaryName[key]. Except that the get method returns None if the key is not in the dictionary rather than raising an exception.

pop(key)-Removes the item for the key and returns its value. The pop(key) method is the same as
del dictionaryName[key[

popitem( )- Returns a randomly selected key/value pair as a tuple and removes the selected item.

Question 22

Which one of these dictionaries are created correctly?
d = {1:[1, 2], 3:[3, 4]} 
d = {[1, 2]:1, [3, 4]:3}  
d = {(1, 2):1, (3, 4):3} 
d = {1:"john", 3:"peter"} 
d = {"john":1, "peter":3} 

If any are incorrect, explain why it is incorrect?

Answer 22

d = {1:[1, 2], 3:[3, 4]}  # Correct
#d = {[1, 2]:1, [3, 4]:3}  # Incorrect, key must be immutable
d = {(1, 2):1, (3, 4):3}  # Correct
d = {1:"john", 3:"peter"} # Correct
d = {"john":1, "peter":3} # Correct

I am assuming that keys must be immutable and values are able to be mutated. Keys are immutable because it is the ‘index’ of the dictionary.

Question 23

What can you use to transverse all elements in a set?

Answer 23

A for loop