Selection

Programs make choices

• Selection means the program picks what to do based on a condition.
• A condition is a question that is True or False.
• This is a key idea in AP CSP: code that decides.

if / elif / else

• if runs its block only when the condition is True.
• elif ("else if") checks another condition if the ones above were False.
• else runs when none of the conditions were True.

hour = 14
if hour < 12:
    print("Morning")
elif hour < 18:
    print("Afternoon")
else:
    print("Evening")

Comparisons make conditions

• == equal, != not equal, < > <= >=.
• == tests if two values are equal; a single = stores a value.
• The result of a comparison is True or False.

score = 72
print(score >= 50)
print(score == 100)

Boolean logic: and / or / not

• and is True only when both sides are True.
• or is True when at least one side is True.
• not flips it: not True is False.

age = 16
if age >= 13 and age <= 19:
    print("Teenager")
else:
    print("Not a teenager")

In AP CSP pseudocode

• Python if/else matches CB's IF(condition){ } ELSE { }.
• CB uses words for logic: AND, OR, NOT.
• DISPLAY = print, ← = =.

IF (score >= 50)
{
    DISPLAY "Pass"
}
ELSE
{
    DISPLAY "Fail"
}

IF ((age >= 13) AND (age <= 19))
{
    DISPLAY "Teenager"
}

Common mistakes

• Compare with ==, not =.
• Indent the block that runs when the condition is true.

Now you try

• Read each task to see what to print or check.
• Match the output text exactly.