Chapter 2 - Definitions

Question 1

Assignment statement

Answer 1

A statement that assigns a VALUE to a name (VARIABLE). To the left of the assignment operator, =, is a NAME. To the right of the assignment token is an expression which is evaluated by the Python interpreter and then assigned to the NAME. The difference between the left and right hand sides of the assignment statement is often confusing to new programmers.

In the following assignment:
n = n + 1
n plays a very different role on each side of the =. On the right it is a VALUE and makes up part of the EXPRESSION which will be evaluated by the Python interpreter before assigning it to the name on the left.

Question 2

Define assignment token

Answer 2

= is Python’s assignment token, which should not be confused with the mathematical comparison operator using the same symbol.

Question 3

Define class

Answer 3

see data type below

Question 4

Define comment

Answer 4

Info in a program that is meant for other programmers (or anyone reading the source code) and has no effect on the execution of the program

Question 5

Define data type

Answer 5

A set of values. The type of a value determines how it can be used in expressions. So far, the types you have seen are integers (int), floating-point numbers (float), and strings (str).

Question 6

Define decrement

Answer 6

Decrease by 1

Question 7

Define evaluate

Answer 7

To simplify an expression by performing the operations in order to yield a single value.

Question 8

Define expression

Answer 8

A combination of operators and operands (variables and values) that represents a single result value. Expressions are evaluated to give that result.

Question 9

Define float

Answer 9

A Python data type which stores floating-point numbers. Floating-point numbers are stored internally in two parts: a base and an exponent. When printed in the standard format, they look like decimal numbers. Beware of rounding errors when you use floats, and remember that they are only approximate values.

Question 10

Define increment

Answer 10

Both as a noun and as a verb, increment means to increase by 1.

Question 11

Define initialization (of a variable)

Answer 11

To initialize a variable is to give it an initial value. Since in Python variables don’t exist until they are assigned values, they are initialized when they are created. In other programming languages this is not the case, and variables can be created without being initialized, in which case they have either default or garbage values.

Question 12

Define int

Answer 12

A Python data type that holds positive and negative whole numbers.

Question 13

Define integer division

Answer 13

An operation that divides one integer by another and yields an integer. Integer division yields only the whole number of times that the numerator is divisible by the denominator and discards any remainder.

Question 14

Define keyword

Answer 14

A reserved word that is used by the compiler to parse program; you cannot use keywords like IF, DEF, and WHILE as variable names.

Question 15

Define modulus operator

Answer 15

Also called remainder operator or integer remainder operator. Gives the remainder after performing integer division.

Question 16

Define object

Answer 16

Also known as a data object (or data value). The fundamental things that programs are designed to manipulate (or that programmers ask to do things for them).

Question 17

Define operand

Answer 17

One of the values on which an operator operates.

Question 18

Define operator

Answer 18

A special symbol that represents a simple computation like addition, multiplication, or string concatenation.

Question 19

Define prompt string

Answer 19

Used during interactive input to provide the user with hints as to what type of value to enter.

Question 20

Define reference diagram

Answer 20

A picture showing a variable with an arrow pointing to the value (object) that the variable refers to. See also state snapshot.

Question 21

Define rules of precedence

Answer 21

The set of rules governing the order in which expressions involving multiple operators and operands are evaluated.

Question 22

Define state snapshot

Answer 22

A graphical representation of a set of variables and the values to which they refer, taken at a particular instant during the program’s execution.

Question 23

Define statement

Answer 23

An instruction that the Python interpreter can execute. So far we have only seen the assignment statement, but we will soon meet the IMPORT statement and the FOR statement.

Question 24

Define str

Answer 24

A Python data type that holds a string of characters.

Question 25

Define type conversion function

Answer 25

A function that can convert a data value from one type to another.

Question 26

Define value

Answer 26

A number or string (or other things to be named later) that can be stored in a variable or computed in an expression.

Question 27

Define variable

Answer 27

A name that refers to a value.

Question 28

Define variable name

Answer 28

variable name
A name given to a variable. Variable names in Python consist of a sequence of letters (a..z, A..Z, and _) and digits (0..9) that begins with a letter. In best programming practice, variable names should be chosen so that they describe their use in the program, making the program self documenting.