Which of these logic constructs most efficiently (in terms of code conciseness and variable reuse) allows you to select and execute one code block out of 3 or more based on the value of a single variable?

Which of these logic constructs most efficiently (in terms of code conciseness and variable reuse) allows you to select and execute one code block out of 3 or more based on the value of a single variable?

• while
• for
• if
• switch

EXPLANATION

if statement

People make decisions on a daily basis. What should I have for lunch? What should I do this weekend? Every time you make a decision you base it on some criterion. For example, you might decide what to have for lunch based on your mood at the time, or whether you are on some kind of diet. After making this decision, you act on it. Thus decision-making is a two step process – first deciding what to do based on a criterion, and secondly taking an action.
Decision-making by a computer is based on the same two-step process. In Python, decisions are made with the if statement, also known as the selection statement. When processing an if statement, the computer first evaluates some criterion or condition. If it is met, the specified action is performed. Here is the syntax for the if statement:

if condition:
    if_body

When it reaches an if statement, the computer only executes the body of the statement only if the condition is true. Here is an example in Python, with a corresponding flowchart:

if age < 18:
    print("Cannot vote")