Chapter 7

Question 1

What is a sequence?

Answer 1

An Object that contains multiple items of data

Question 2

What is a list?

Answer 2

An object that contains multiple data items
EX: even_numbers = [2, 4, 6, 8, 10]
info = [‘Alicia’, 27, 1550.87}

Question 3

What is an element?

Answer 3

Each object that is stored in a list

Question 4

How do you display an entire list?

Answer 4

Use the print function:
numbers = [5, 10, 15, 20]
print(numbers)

Question 5

How would you convert certain objects to lists using range:

Answer 5

numbers = list(range(5))

• The range function is called with 5 passed as an argument. The function returns an iterable containing the values 0, 1, 2, 3, 4.
• The iterable is passed as an argument to the list() function. – -The list() function returns the list [0, 1, 2, 3, 4].
• The list [0, 1, 2, 3, 4] is assigned to the numbers variable.

Question 6

What is a repetition operator?

Answer 6

when the operand on the left side of the * symbol is a sequence (such as a list) and the operand on the right side is an integer,
EX: 
1  >>> numbers = [1, 2, 3] * 3 [Enter]
 2  >>> print(numbers) [Enter]
 3  [1, 2, 3, 1, 2, 3, 1, 2, 3]
 4  >>>

Question 7

How do you access a list with a for loop?

Answer 7

numbers = [1, 2, 3, 4]
for num in numbers:
print(num)
The numbers variable references a list with four elements, so this loop will iterate four times. The first time the loop iterates, the num variable will reference the value 1, the second time the loop iterates, the num variable will reference the value 2, and so forth.

-num variable value has no effect on the output

Question 8

What is an index ?

Answer 8

Each element in a list has an index that specifies its position in the list. Indexing starts at 0, sothe index of the first element is 0
print(my_list[0], my_list[1], my_list[2], my_list[3])
EX #2:
index = 0
while index < 4:
print(my_list[index])
index += 1

Question 9

What is an indexError exception?

Answer 9

raised if you use an invalid index with a list.

Question 10

What is the len function in python?

Answer 10

returns the length of a sequence, such as a list.
EX: my_list = [10, 20, 30, 40]
size = len(my_list)

Question 11

How do you use a len and range function to get the indexes in a list?

Answer 11

1  names = ['Jenny', 'Kelly', 'Chloe', 'Aubrey']
 2  for index in range(len(names)):
 3      print(names[index])

Question 12

What does mutable mean?

Answer 12

Lists in python can be changed
EX: Line 3 in this code rewrites an index:
1  numbers = [1, 2, 3, 4, 5]
 2  print(numbers)
 3  numbers[0] = 99
 4  print(numbers)

Question 13

How do you concatenate a list?

Answer 13

Use the + operator:
list1 = [1, 2, 3, 4]
 list2 = [5, 6, 7, 8]
 list3 = list1 + list2
OR use += to concatenate one list to the other
list1 = [1, 2, 3, 4]
 list2 = [5, 6, 7, 8]
 list1 += list2

Question 14

What is a slice?

Answer 14

A span of items that are taken from a sequence
EX: list_name[start : end]
days = [‘Sunday’, ‘Monday’, ‘Tuesday’, ‘Wednesday’,
‘Thursday’, ‘Friday’, ‘Saturday’]
mid_days = days[2:5]
[‘Tuesday’, ‘Wednesday’, ‘Thursday’]
(Does not include end but includes start)

Question 15

How do you slice a list with a step value?

Answer 15

[1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
&raquo_space;> print(numbers[1:8:2]) [Enter]
[2, 4, 6, 8]
-Step value of 2 to get every other item form the list

Question 16

What does the in operator do in Python?

Answer 16

-Used to determine whether an item is contained in a list
EXAMPLE:
9 search = input(‘Enter a product number: ‘)
10
11 # Determine whether the product number is in the list.
12 if search in prod_nums:
13 print(f’{search} was found in the list.’)
14 else:
15 print(f’{search} was not found in the list.’)

Question 17

What does the not in operator do in Python?

Answer 17

Determines if an item is not inside of a list
EXAMPLE:
if search not in prod_nums:
print(f’{search} was not found in the list.’)
else:
print(f’{search} was found in the list.’)

Question 18

What does the append method do?

Answer 18

Adds items onto a list:

name_list.append(name)

Question 19

What does the index method do?

Answer 19

Shows the index of where an item is located in a list
EXAMPLE:
Item_index = food.index(item)

Question 20

What does the insert method do?

Answer 20

Allows you to insert an item into a list at a specific position.
-Two arguments get passed into the insert method: index specifying where the item should be inserted and the item you want to insert
EXAMPLE:
name.insert(0, ‘Joe’)

Question 21

What does the sort method do?

Answer 21

Rearranges the elements of a list so they appear in ascending order (from the lowest value to the highest value)
EXAMPLE: my_list.sort()

Question 22

What does the remove method do?

Answer 22

Removes an item from the list. You pass an item to the method as an argument and the first element containing that item is removed.
EXAMPLE:
food.remove(item)

Question 23

What does the reverse method do?

Answer 23

Reverses the order of the items in the list
EXAMPLE:
my_list.reverse()

Question 24

What does the del statement do?

Answer 24

Allows you to remove an element from a specific index REGARDLESS of the item stored in that index
EXAMPLE:
del my_list[2]

Question 25

What is the min and max functions?

Answer 25

Min function: Accepts a list as an argument and returns the item that has the lowest value
Max function: Accepts a list as an argument and returns the item that has the highest value

EXAMPLE:
print(min(my_list))

Question 26

How do you create a copy of a list that is a separate entity from that list?

Answer 26

Use the append item as shown here:

list2 = [] + list1

Question 27

How do you use the random module with a list?

Answer 27

import random

random.choices(numbers, k=3)

Question 28

What does the writelines method do?

Answer 28

8      # Open a file for writing.
  9      outfile = open('cities.txt', 'w')
 10
 11      # Write the list to the file.
 12      outfile.writelines(cities)
 13
 14      # Close the file.
 15      outfile.close()

-saves the contents of a list to a file

Question 29

What is a list comprehension?

Answer 29

-an expression that reads an input list, using the values of the input list to produce an output list
EXAMPLE:
list1 = [1, 2, 3, 4]
list2 = [item for item in list1]

EX 2: shows length of strings in first list

str_list = [‘Winken’, ‘Blinken’, ‘Nod’]
len_list = [len(s) for s in str_list]

EX 3: Makes a new list of integers less than 10:

list1 = [1, 12, 2, 20, 3, 15, 4]
list2 = [item for item in list1 if item < 10]

Question 30

What are nested, or two dimensional lists?

Answer 30

Lists inside of lists

1 &raquo_space;> students = [[‘Joe’, ‘Kim’], [‘Sam’, ‘Sue’], [‘Kelly’, ‘Chris’]] [Enter]

Question 31

How would you write a for loop for nested loop?

Answer 31

10 for row in values:
11 for element in row:
12 print(element)
13

Question 32

What is a tuple?

Answer 32

A tuple is a sequence like a list except it cannot be changed

• A tuple is written with parenthesis instead of brackets
• Tuples supports all the same operations as a list except those that change the list

> > > my_tuple = (1, 2, 3, 4, 5) [Enter]
print(my_tuple) [Enter]
(1, 2, 3, 4, 5)

Question 33

What is the reason for tuples?

Answer 33

Processing tuples is faster than processing a list

It is also safer because it definitely can’t be changed

Question 34

What does the built-in list() function do? What does a built-in tuple() function do?

Answer 34

-Converts a tuple to a list
-Converts a list to a tuple
EXAMPLE

2 &raquo_space;> number_list = list(number_tuple) [Enter]
3 &raquo_space;> print(number_list) [Enter]
4 [1, 2, 3]
5 &raquo_space;> str_list = [‘one’, ‘two’, ‘three’] [Enter]
6 &raquo_space;> str_tuple = tuple(str_list) [Enter]

Question 35

What does the matplotlib package do?

Answer 35

library for creating two-dimensional charts and graphs
Not part of python library so must be installed separately
Useful for different graphical calculations

Question 36

How do you import pyplot from mathplotlib?

Answer 36

import matplotlib.pyplot