Chapter 3 part 5

Question 1

Lets recap what the range function does

Answer 1

Produces a sequence of consecutive integers from 0 up to, but NOT including the arguments value.

Question 2

What are the 2 arguments of the range function?

Answer 2

1. produces a sequence of consecutive integers 0 up to but NOT including the artument’s value
2. the second argument produces also a consecutive integers from the FIRST argument’s value up to but NOT including the second argument’s value
   Ex:
   for number in range (5, 10):
   ….print(number, end=’ ‘)

5 6 7 8 9

Notice that 10 was not included

Question 3

What are the 3 arguments of the range function?

Answer 3

Produces a sequence of integers from its first argument’s value up to, but not including, the second argument’s value, incrementing by the third argument’s value (known as the step
Ex:

for number in range(0, 10, 2):
…print(number, end=’ ‘)

0 2 4 6 8

Notice that we did not include 10 in our result, instead, the increments start at 2 and go up 2 at a time until it reaches as close to the second argument (10) as possible

Question 4

What happens if the third argument is negative in a range function?

Answer 4

The sequence progresses from the first argument’s value down to, but not including the second argument’s value, decrementing by the third argument’s value as in:

for number in range(10, 0, -2):
…print(number, end=’ ‘)

10 8 6 4 2

Question 5

T/F

Function call range(1, 10) generates the sequence 1 through 10

Answer 5

False. Function call range(1, 10) generates the sequence 1 through 9

Question 6

What happens if you try to print the items in range (10, 0, 2)?

Answer 6

Nothing displays because the step is not negative. This is not a fatal error.

Question 7

Things to know about decimals for menetary amounts in Python

Answer 7

• Python’s built-in-floating point numbers work well for most applications
• Floating-point values are stored in binary format
• Some floating-point values are represented only approximately when they’re covered to binary

Question 8

What are the Python Standard Library’s modules?

Answer 8

Groups of related capabilities
The decimal module defines type Decimal and its capabilities

Question 9

How do you use capabilities from a module?

Answer 9

You must first import the entire module as in

import decimal

and refer to the Decimal type as decimal.Decimal or you must indicate a specific capability to import using from…import as we do here:

In[4]: from decimal import Decimal

This imports only the type Decimal from the decimal module so that you can use it in your code

You typically create a Decimal from a string

Question 10

What is the >2 mean here: print(f’{year:>2}

Answer 10

The right aligned (>) indicates to align the year to the right and with a field width of 2 character positions

Question 11

What is the ** < 10.2 ** mean here:
print(f’{amount:>10.2f)’)

Answer 11

This aligns the format to the left with <
The format specifier 10.2f states a field width of 10 with a decimal point and 2 digits to the right of the decimal point (.2)
f is for floating-point number
Formatting the amounts this way aligns their decimal points vertically

Question 12

A field width specifies the ___blank___ to use when displaying a value

Answer 12

number of character positions

Question 13

What happens when you execute a break statement in a while or for statement?

Answer 13

It immediately exits that statement
Ex:

for number in range(100):
…if number == 10:
……break
…print(number, end=’ ‘)

0 1 2 3 4 5 6 7 8 9

Notice that the if statement tells the program to break or terminate when number is 10 although the range is from 0-99

Question 14

What does continue do in a while or for statement?

Answer 14

The loop skips the remainder of the loop’s suite
In a while condition, it is tested to determine whether the loop should continue executing
in a for condition, the loop processes the next item in the sequence (if any)

for number in range(10):
…if number ==5:
……continue
…print(number, end=’ ‘)

0 1 2 3 4 5 6 7 8 9

Notice that 5 was not included in the result

Question 15

Use Boolean operators and, or, not to combine 2 conditions example

Answer 15

conditions:
- gender == ‘Female’
- age >= 65
Now combine

gender = ‘Female’
age = 70
if gender == ‘Female’ and age >= 65:
…print(‘Senior female’)

Senior female

Notice we used the Boolean operator and to combine gender and age here
It tests if these conditons are true. In this example, since both are true, expression 1 and expression 2 result in a true condition

Question 16

Write an example of a Boolean operator or example

Answer 16

conditions:
- semester average >= 90
- final exam >= 90
Now combine

semester_average = 83
final_exam = 95
if semester_average >= 90 or final_exam >= 90:
…print(‘Student gets an A’)

Student gets an A

The or tests if one or both of the 2 conditions are true

Question 17

What is the difference when you use an and Boolean operator?

Answer 17

Python stops evaluating the condition if the entire condition is false
Same thing happens when Python is evaluating an or expression. It stops evaluating it as soon as it knows the entire condition is true
This is called a short-circuit evaluation

Ex:
gender == ‘Female’ and age >= 65

Stops evaluating completely if gender is not equal to ‘Female’

semester_average >= 90 or final_exam >= 90

Stops evaluating completely if semester_average is greater than or equal to 90 b/c then it’s true. If it’s less then execution continues in order to find out if condition is true with the final_exam

Question 18

What does the Boolean operator not do?

Answer 18

It ‘reverses’ the meaning of a conditioin - true becomes false and false becomes true
You can avoid using not by using a more known convension such as != which is used to check if 2 values are not equal. It returns true if the values on either side of the operator are different and false if they are the same
Ex:

grade = 87
if grade != -1
…print(‘The next grade is’, grade)

The next grade is 87

Question 19

Assume that i = 1, j = 2, k = 3, m = 2
What does each of the following conditions display?
a. (i >= 1) and (j < 4)

b. (m <= 99) and (k < m)

c. (j >= i) or (k == m)

d. (k + m < j) or (3 - j >= k)

e. not (k > m)

Answer 19

a. true
b. false
c. true
d. false
e. false

Question 20

What are the 3 measures of central tendency?

Answer 20

Mean
Median
Mode

Each represent a ‘central’ value in a set of values
- A value which is in some sense typical of the others

Question 21

What do the sum and len functions do?

Answer 21

sum adds integers
len returns the numbers of total integers
Ex to calc an average:

grades = [85, 93, 45, 89, 85]

sum(grades) / len(grades)
79.4