Chapter If statement, Python

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What types of relationships between values can you test with relational operators?

> greater than < less than >= greater than or equal to <= less than or equal to == equal to != not equal to

What is a flag variable?

A Boolean variable that when the flag value is true it means the condition exists, while a false value of the flag means the condition does not exist.

What values can you assign to a bool variable?

A bool variable can only store one of two possible values: True or False. Example: x = true; y = false

What is a compound Boolean expression?

A combination of two or more Boolean expressions using logical operators such as "and", ""or", and "not".

The following shows a combination of the values true and false connected by a logical operator. Indicate whether the result of such a combination is true or false. False and False

False

The following shows a combination of the values true and false connected by a logical operator. Indicate whether the result of such a combination is true or false. False and True

False

The following shows a combination of the values true and false connected by a logical operator. Indicate whether the result of such a combination is true or false. False or False

False

The following shows a combination of the values true and false connected by a logical operator. Indicate whether the result of such a combination is true or false. True and False

False

The following shows a combination of the values true and false connected by a logical operator. Indicate whether the result of such a combination is true or false. not True

False

You can write any program using only sequence structures. T or F

False

What is a flag and how does it work?

Flags are Boolean variables that indicate whether a specific condition exists or not. When the flag value is true it means the condition exists, while a false value of the flag means the condition does not exist.

Explain what is meant by the term "conditionally executed."

Is a set of statements that are executed only when a certain condition is true. If the condition is false they will not be executed. Also called a single alternative decision structure.

flag

a variable that signals when some condition exists in the program

The following shows a combination of the values true and false connected by a logical operator. Indicate whether the result of such a combination is true or false. True or True

True

The following shows a combination of the values true and false connected by a logical operator. Indicate whether the result of such a combination is true or false. not False

True

Dual Alternative Decision Structure

has two possible paths of execution one path is taken if the condition is true and another is taken if the condition is false

You use a(n) _____ statement to write a single alternative decision structure. a. test-jump b. if c. if-else d. if-call

if

What happens when the if statement executes?

the condition is tested if it is true the statements in the block are executed if it is false the statements in the block are skippped

What is used to write a single alternative decision structure?

the if statement

What values can be assigned to a bool variable?

true or false

What are the following operators? 1. greater than 2. less than 3. greater than or equal to 4. less than or equal to 5. equal to 6. not equal to

1. greater than > 2. less than < 3. greater than or equal to >= 4. less than or equal to <= 5. equal to == 6. not equal to !=

Control structure

a logical design that controls the order in which a set of statements execute

Sequence Structure

a set of statements that execute in the order that they appear

Briefly describe how the "and" operator works.

An expression formed by the "and" operator is true only when both the 'first' and 'second' sub expressions are true. If the left sub expression is false then it will not check the right sub expression because the overall expression has already been determined as false, this is called "short cut evaluation".

Briefly describe how the "or" operator works.

An expression formed by the "or" operator is false only when both the 'first' and 'second' sub expressions are false. If the left sub expression is true then it will not check the right sub expression because the overall expression has already been determined as true, this is called "short cut evaluation".

A(n) _____ expression has a value of either true or false. a. binary b. decision c. unconditional d. Boolean

Boolean

What is a Boolean expression?

Boolean expressions check the truth of an expression, it checks whether the expression is true or false.

What is a decision structure?

Decision structures are control structures which provide a different set of instructions to be executed based on different choices made by the user.

How does a dual alternative decision structure work?

Dual alternative decision structure is a control structure with two possible paths of execution. The program will follow one path if condition equals true and another if condition equals false.

You need to test a condition and then execute one set of statements if the condition is true. If the condition is false, you need to execute a different set of statements. What structure will you use?

Dual alternative decision structure.

A program can be made of only one type of control structure. You cannot combine structures. T or F

False

A single alternative decision structure tests a condition and then takes one path if the condition is true, or another path if the condition is false. T or F

False

What is a single alternative decision structure?

Single alternative decision structure is a control structure that only provides one alternative path of execution. If the condition is true the alternative path is taken, if the condition is false the alternative path is skipped.

What is a control structure?

The logical design which is used to control or handle the execution order of statements.

A compound Boolean expression created with the "and" operator is true only when both subexpressions are true. T or F

True

A decision structure can be nested inside another decision structure. T or F

True

The following shows a combination of the values true and false connected by a logical operator. Indicate whether the result of such a combination is true or false. False or True

True

The following shows a combination of the values true and false connected by a logical operator. Indicate whether the result of such a combination is true or false. True and True

True

The following shows a combination of the values true and false connected by a logical operator. Indicate whether the result of such a combination is true or false. True or False

True

When you write an if-else statement, under what circumstances do the statements that appear after the else clause execute?

When the if condition is false the program follows the else clause.

Conditionally Executed

action that is performed only when a certain condition is true

Compare strings

allows you to create decision structures that test the value of a string

A compound Boolean expression created with the _____ operator is true only if both of its subexpressions are true. a. and b. or c. not d. both

and

When determining whether a number is inside a range, which logical operator is it best to use?

and

Explain how short-circuit evaluation works with the "and" and "or" operators.

and operator short circuit - If the left sub expression is false then it will not check the right sub expression because the overall expression has already been determined as false. or operator short circuit - If the left sub expression is true then it will not check the right sub expression because the overall expression has already been determined as true.

if clause

begins with the word if and is followed by the "condition"

How do we test more than one condition?

by nesting a decision structure inside another decision structure

Decision or Selection structures

can execute a set of statements only under certain circumstances

A _____ structure can execute a set of statements only under certain circumstances. a. sequence b. circumstantial c. decision d. Boolean

decision

Relational Operator

determines whether a specific relationship exists between two values

A(n) _____ structure tests a condition and then takes one path if the condition is true, or another path if the condition is false. a. if statement b. single alternative decision c. dual alternative decision d. sequence

dual alternative decision

condition

expression that will be evaluated as either true or false

Boolean expression

expressions tested by the if statement

A _____ is a Boolean variable that signals when some condition exists in the program. a. flag b. signal c. sentinel d. siren

flag

Example if-elif-else statement

if condition1: statement statement elif condition2: statement statement else: statement statement

Example if-else statement

if condition: statement statement else: statement statement

sample if statement

if condition: statement statement

You use a(n) _____ statement to write a dual alternative decision structure. a. test-jump b. if c. if-else d. if-call

if-else

What statement do you use in Python to write a dual alternative decision structure?

if..... else

and, or, and not are _____ operators. a. relational b. logical c. conditional d. ternary

logical

The _____ operator takes a Boolean expression as its operand and reverses its logical value. a. and b. or c. not d. either

not

A compound Boolean expression created with the ____ operator is true if either of its subexpressions is true. a. and b. or c. not d. either

or

Single Alternative Decision Structure

provides only one alternative path of execution

The symbols >, <, and == are all _____ operators. a. relational b. logical c. conditional d. ternary

relational

A _____ structure provides one alternative path of execution. a. sequence b. single alternative decision c. one path alternative d. single execution decision

single alternative decision

if statement

used to create a decision structure, which allows a program to have more than one path of execution Causes one or more statements to execute only when a boolean expression is true

nested block

when a block of code that is inside another block of code is indented

if-else statement

will execute one block of statements if its condition is true, or another block if its condition is false


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