Chapter 2: Variables, Expressions and Statements | Glossary

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.

Question 2

assignment token

Answer 2

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

Question 3

comment

Answer 3

Information 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 4

data type

Answer 4

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 5

decrement

Answer 5

Decrease by 1.

Question 6

evaluate

Answer 6

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

Question 7

expression

Answer 7

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

Question 8

float

Answer 8

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.

Question 9

increment

Answer 9

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

Question 10

initialization (of a variable)

Answer 10

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 11

int

Answer 11

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

Question 12

integer division

Answer 12

Uses //. 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 13

keyword

Answer 13

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 14

modulus operator

Answer 14

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

Question 15

object

Answer 15

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 16

operand

Answer 16

One of the values on which an operator operates.

Question 17

operator

Answer 17

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

Question 18

prompt string

Answer 18

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

Question 19

reference diagram

Answer 19

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

Question 20

rules of precedence

Answer 20

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

Question 21

state snapshot

Answer 21

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 22

statement

Answer 22

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 23

str

Answer 23

A Python data type that holds a string of characters.

Question 24

type conversion function

Answer 24

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

Question 25

value

Answer 25

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

Question 26

variable

Answer 26

A name that refers to a value.

Question 27

variable name

Answer 27

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.