Chapter 2 notes 3

Question 1

What uses a condition to decide whether to execute a statement (or a group of statements) with these in comparison operator

Answer 1

Using if statements
If the condition in a given statement is True, the corresponding ‘print’ statement executes; otherwise, it’s skipped

Question 2

When do you use a script?

Answer 2

When you have many statements to execute as a group, you write them as a script stored in a file with the .py extension

Question 3

What’s another word for script?

Answer 3

Programs

Question 4

What are integrated development environments? (IDEs)

Answer 4

They enable you to choose whether to display line numbers

Question 5

What does it mean when a line begins with a #?

Answer 5

A # symbol indicates that the rest of the line is a comment

Question 6

Why would you insert comments to a code?

Answer 6

To improve readability. Also helps other programmers read and understand your code. They do NOT cause the computer to perform any actions when the code executes
A comment can begin to the right of the code on a given line and continue until the end of that line. Such a comment documents the code to its left

Question 7

Docstrings, what are they?

Answer 7

A Docstrings explains the scripts purpose and begins. Ex:
“””Comparing integers using if statements and comparison operators.”””
They are usually found at the beginning of the script.

Question 8

Blank lines, why?

Answer 8

You use blank lines and space characters to make code easier to read. Together, blank lines, space characters and tab characters are known as white space.
Python ignores them but some identification is required

Question 9

How to keep a string together when using more than one line?

Answer 9

You may spread a lengthy statement over several lines with the \ continuation character. Python also allows you to split long code lines in parenthesis without using continuation characters.

Question 10

Suite, explained and common syntax error

Answer 10

An if statement is the condition to test, and a colon (:) is followed by an intended body called a suite. Each suite must contain one or more statements. Forgetting the colon (:) after the condition is a common syntax error.
Python requires you to indent the statements in suites.

Question 11

In if statements, = and ==

Answer 11

= is “assigned”
== is equal to

Question 12

Why use chain comparisons?

Answer 12

To check a value is in range

In[1]: x = 3

In[2]: 1 <= x <= 5
Out[2]: True

In[3]: x = 10

In[4]: 1 <= x <= 5
Out[4]: False

Question 13

You use __________ to document code and improve its readability

Answer 13

Comments

Question 14

T/F the comparison operators evaluate left to right and all have the same level of precedence

Answer 14

False, the operators <, <=, > and >= all have the same level of precedence and evaluate left to right. The operators ++ and != have the same level of precedence and evaluate left to right. Their precedence is lower than that of <, <=, > and >=

Question 15

For any of the operators !=, >= or <=, show that a syntax error occurs if you reverse the symbols in a condition

Answer 15

Question 16

Use all 6 comparison operators to compare the values 5 and 9. Display the values on one line using print

Answer 16

In[2]: print(5 < 9, 5 <= 9, 5 > 9, 5 >= 9, 5 == 9, 5 != 9)
True True False False False True

Question 17

How do you find out what type of input is considered?

Answer 17

In{1]: type(7)
Out[1]: int

You put the input inside the parentheses and press Enter

In[2]: type(2.5)
Out[2]: float

In[3]: type(‘dog’)
Out[3]: str

Question 18

Assigning an object to a variable ______ (associates) that variable’s name to the object

Answer 18

Binds

In[4]: x = 7

In[5]: x + 10
Out[5]: 17

In[6]: x
Out[6]: 7

Question 19

Python uses _______ ________ it determines the type of the object a variable refers to while executing your code.

Answer 19

Dynamic typing

Question 20

What is garbage collection in Python?

Answer 20

When the memory in Python is re-written as an object is bound to another and what it was previously bound to has not been removed and forgotten. This helps ensure that memory is available for new objects you create.

Question 21

Assigning an object to a variable _________ the variable’s name to the object

Answer 21

Binds

Question 22

T/F a variable always references the same object

Answer 22

False, you can make an existing variable refer to a different object and even one of a different type

Question 23

What is the type of expression 7.5 * 3?

Answer 23

Float