Chapter 2 notes

Question 1

Python style convention for binary operators

Answer 1

Adding a space on each side of the assignment symbol = and binary operators like + to make programs more readable

Question 2

Identifier

Answer 2

A variable name such as X, is an identifier. It may consist of letters, digits and underscores (_) but not begin with a digit.

Question 3

Is Python case sensitive?

Answer 3

Yes, so number and Number are different identifiers because one begins with a lowercase and the other with upper

Question 4

Type

Answer 4

Each value has a type that indicates the kind of data the value represents.
In [7]: type(x)
Out[7]: int

In[8]: type(19.5)
Out[8]: float

Floating-point number (float)

Question 5

Floating-point number

Answer 5

A number with a decimal point, so Python displays float

Question 6

A _______ performs a task when you _______ it by writing its name, followed by parthenesis, ()

Answer 6

Function
Call

Question 7

The parenthesis contain the functions _______ —the data that the type function needs to perform its task

Answer 7

Argument

Question 8

T/F The following are valid variable names: 3g, 87 and score_4

Answer 8

False. Because they begin with a digit, 3g and 87 are invalid names

Question 9

T/F Python treats y and Y as the same integer

Answer 9

False, Python is case sensitive, so y and Y are different identifiers

Question 10

Write the exponential operator

Answer 10

**

Question 11

True division vs Floor division

Answer 11

True division: divides a numerator by a denominator and yields a floating-point number with a decimal point
In[5]: 7 / 4
Out[5]: 1.75

Floor division: divides a numerator by a denominator, yielding the highest integer that’s not greater than the result
In[6]: 7 // 4
Out[6]: 1
Python truncates (discards) the fractional part

Question 12

What would be the answer for
In[9]: -13 // 4

Answer 12

Out[9]: -4
Floor division gives the closes integer that’s not greater than -3.25 which is -4

Question 13

What happens when you divide by 0 with / or //?

Answer 13

Not allowed and results in an exception - a sign that a problem occurred
Python reports an exception with a traceback

Question 14

What does a traceback do?

Answer 14

It indicates that an exception of type ZeroDivisionError occurred-most exception names end with Error.

Question 15

In this image, where is the exception located?

Answer 15

The snippet number that caused the exception is specified by the 10 in the line

<ipython-input-10-cd759d3fcf39> in <module>()
</module></ipython-input-10-cd759d3fcf39>

Question 16

Where does it show the code that caused the exception?

Answer 16

The line that begins with
———-> 1 shows the code that caused the exception

Question 17

Where does it show the exception that occurred?

Answer 17

Followed by the colon (:) and an error message with more information about the exception

ZeroDivisionError: division by zero

Question 18

An exception also occurs if you try to use a variable that you have not yet created

Answer 18

Question 19

How does a remainder operator (%) work?

Answer 19

It will yield the remainder after the left operant is divided by the right operand:
In[12]: 17 % 5
Out[12]: 2

17 divided by 5 yields a quotient of 3 and a remainder of 2. This operator is mostly common used with integers but also can be used with other numeric types like 7.5 % 3.5

Question 20

Redundant parenthesis

Answer 20

If the presence and absence yields the same result

Question 21

Rules of operator precedence

Answer 21

Generally the same as those in algebra. Total of 4
1. Expressions in parenthesis evaluate first. Nested parenthesis ( a / (b - c)), the expression in the innermost parenthesis (b - c) evaluates first
2. Exponential operations evaluate next. If several, Python applies them from right to left
3. Multiplication, division and modulus operations evaluate next. All are on the same level of precedence and are evaluated from left to right
4. Addition and subtraction operations evaluate last. Both are on same level of precedence and will be evaluated from left to right

Question 22

Operators’ grouping

Answer 22

When we have a + b + c, since all are on same level of precedence, we will evaluate from left to right in a manner of groups
So we first do a + b
Then that result + c

Question 23

Exponential operator grouping

Answer 23

This is the only one that groups from right to left

Question 24

What is a mixed-type expression?

Answer 24

Expressions containing an integer and a floating-point number. These always produce a floating-point number.

Question 25

Given that y = ax^3 + 7, which of the following is not a correct statement for this equation?
A. Y = a * x * x * x + 7
B. Y = a * x ** 3 + 7
C. Y = a * (x * x * x) + 7
D. Y = a * x * (x * x + 7)

Answer 25

D. Is incorrect

Question 26

T/F in nested parentheses, the expression in the innermost pair evaluates last

Answer 26

False, the expression in the innermost parentheses evaluates first

Question 27

Evaluate the expression 3 * (4 - 5) with and without parentheses. Are the parentheses redundant?

Answer 27

No
With will yield -3
Without will yield 7

Question 28

Evaluate the expression 4 ** 3 ** 2, (4 ** 3) ** 2 and 4 ** (3 ** 2). Are there any parentheses redundant?

Answer 28

In[3]: 4 ** 3 ** 2
Out[3]: 262144

In[4]: (4 ** 3) ** 2
Out[4]: 4096

In[5]: 4 ** (3 ** 2)
Out[5]: 262144

Only the last expression is redundant