Chapter 7 - Lists and Tuples

Question 1

What is a sequence

Answer 1

an object that contains multiple items of data

the items are stored in sequence, one after another

Question 2

Python provides different types of sequences including lists and tuples. The difference between these:

Answer 2

a list is mutable (changeable)

a tuple is immutable (unchangeable)

Question 3

What is a list:

Answer 3

an object that contains multiple data items

can hold items of different types

the items are enclosed in brackets and separated by commas
list = [‘item1’,’item2’,’item3’]

The print function can be used to display an entire list

list() function can convert certain types of objects into lists

Question 4

what is an element

Answer 4

an item stored in a list

format:
list = [‘item1’,’item2’,’item3’]

Question 5

repetition operator:

Answer 5

makes multiple copies of a list and joins them together.

the * symbol is a repitition operator when applied to a sequence and an integer.

sequence is left operand, number is right

format:
list*n
you can iterate over a list using a for loop

format:
for x in list:

Question 6

what is an index:

Answer 6

a number specifying the position of an element in a list.
enables access to individual element in list
index of first element in list is 0 and the last is -1
negative indexes identify positions relative to the end of the list.

-1 is the last element of the list, -2 is the second to last, etc.

Question 7

Do white spaces also take up index positions?

Answer 7

yes

Question 8

how is an index exception raised

Answer 8

if an invalid index is used

Question 9

what does the len() function do?

Answer 9

returns the length of a sequence such as a list
example: size = len(my_list)

returns the # of elements in the list, so the index of last element is len(list)-1
can be used to prevent an index error exception when iterating over a list with a loop

Question 10

LISTS ARE MUTABLE:

what is a mutable sequence

Answer 10

the items in the sequence can be changed

example:
list[1] = new_value

can be used to assign a new value to a list element

Question 11

concatenation:

Answer 11

joining two things together
+, +=

Question 12

what is an empty list?

Answer 12

a list that contains no elements

example:
list = []

Question 13

List slicing

slice:

Answer 13

a span of items that are taken from a sequence

format: list[start:end]

Question 14

span:

Answer 14

a list containing copies of each element. from start up to, but NOT INCLUDING, end.

if start not specified, 0 is used. if end not specified, len(list) is used for end index

Question 15

What does this do:

item in list

Answer 15

returns true if item is in the list.

the in operator will help to determine whether an item is contained in a list

similarly you can use not in to see if an item is not in a list

Question 16

append(item)

Answer 16

used to add items to the end of a list, by modifying the original list

Question 17

extend(item)

Answer 17

takes a list as an argument and appends all of the elements.

Question 18

sort(item)

Answer 18

used to sort the elements of the list in ascending order

t = [d,c,e,b,a]

t.sort()
t
[a,b,c,d,e]

Question 19

index(item)

Answer 19

used to determine where an item is located in a list.

returns the index of the 1st element in the list containing item.

raised value error exception if item not in list

Question 20

insert(index,item)

Answer 20

used to insert item at position index in the list

Question 21

del statement

Answer 21

removes an element from a specific index in a list

format: del list[i]

if you delete a list it is gone

Question 22

min and max functions:

Answer 22

built-in functions that returns the item that has the lowest or highest value in the sequence

sequence is passed as an argument

Question 23

remove(item)

Answer 23

removes the first occurrence of item from the list. Value error raised if item not found in list

Question 24

reverse()

Answer 24

reverses the order of the items in the list

Question 25

2 methods to copy a list:

Answer 25

1.) creating a new empty list and using a for loop to add a copy of each element from the original list to the new list

2.) creating a new empty list and concatenations the old list to the new empty list

Question 26

s.capitilize()

Answer 26

capitilzes the strings in a list ( you can use a function for this) a for loop

def capitilize_all(t):
res = []
for s in t:
res.append(s.capitilize())
return res

Question 27

isupper()

Answer 27

can be used to check and see if the string contains only upper case letters

Question 28

sum()

Answer 28

can add up all of the elements in a list. an operation like this that combines a sequence of elements into a single value is sometimes called REDUCE.

Question 29

List comprehension:

Answer 29

a concise expression that creates a new list by iterating over the elements of an existing list

list1= [1,2,3,4]
list2=[]

for item in list1:
list2.append(item)

or using list comprehension:

list1= [1,2,3,4]
list2 = [item for item in list1]

Question 30

2 dimensional list

Answer 30

a list that contains other lists as its elements.

(AKA nested lists)
common to think of these as having rows and columns

useful for working with multiple sets of data.

to process these lists need to use two indexes.

typically use nested loops to process

Question 31

tuple:

Answer 31

an immutable sequence and very similar to a list

once created cannot be changed

format:
tuple_name = (item1,Item2)

Tuples support operations as lists:
-subscript indexing for retrieving elements
-methods such as index
-built in functions: len,max,min
-slicing expressions
-the in,+,and * operators

Question 32

Tuples do not support:

Answer 32

-append
-remove
-insert
-reverse
-sort

Question 33

Advantages for using tuples over lists

Answer 33

1.) processing is faster than processing lists

2.) tuples are safer

Question 34

list() function

Answer 34

converts tuple to list

Question 35

tuple()

Answer 35

converts list to tuple

Question 36

pop(item)

Answer 36

if you know the index of an element use pop(this is rare) to delete it. if you dont provide an index it deletes and returns the last element. pop will retain the value in a variable

Question 37

remove(item)

Answer 37

removes the first occurrence of item in the list

Question 38

reverse()

Answer 38

reverses the order of the elements in the list

Question 39

del statement

Answer 39

removes an element from a specific index in a list

del list [2]

Question 40

is operator

Answer 40

used to check whether two variables refer to the same object

if:
a = “banana”
b = “banana”

a is b
true

but when you create two lists, you get two objects. even if the elements are the same, the statement would then be false

Question 41

A list can contain another list, the nested list still counts as a single element. True or false

Answer 41

true.

example:

[‘spam’,1,[‘brie’,’ryan’,’poll’],[1,2,3]]

the inside list is only one element making a total of 4 elements