Section Summary: Control Flow

Activities 1.10 – 1.17. Use this to review, or to fill in a definition you missed.

1. Booleans and Conditions

A comparison produces a boolean, and an if statement uses that boolean to decide whether to run a block. In Python, indentation is what marks the block.

Boolean: A value that is either True or False.
Comparison Operator: An operator like == or >= that compares two values and produces a boolean.
if Statement: Runs a block of code only when its condition is True.
Condition: The boolean expression an if statement checks.
Code Block: A group of statements, marked in Python by indentation.
Logical Operator: and, or, and not — combine or invert booleans.

2. Branching

An if can be extended into a chain. Only the first branch whose condition is true will run, and this is also where you first imported the random module.

else: Runs when every condition before it was False.
elif: Chains another condition onto an if — only the first true branch runs.

3. Nesting

A conditional can live inside another conditional, which lets you ask a follow-up question only when the first answer was yes.

Nesting: Placing one code block (like an if) inside another.
pass: A placeholder statement that does nothing — used where Python requires a block but you have nothing to put there yet.

4. while Loops

A while loop repeats as long as its condition holds. Something inside the loop has to change that condition, or it never ends.

Iteration: Repeating a block of code multiple times.
while Loop: Repeats its block as long as its condition is True.
Infinite Loop: A loop whose condition never becomes False, so it never stops.
Sentinel Value: A specific value a loop watches for to know when to stop.
Built-in Function: A function Python already provides, like round() — avoid naming variables the same thing.

5. for Loops

When you know how many times to repeat, a for loop is the better fit. range() supplies the numbers to count through.

for Loop: Repeats its block once for each value in a sequence.
range(): Generates a sequence of numbers for a for loop to count through.

6. Nested Loops

A loop inside a loop runs the inner block once for every combination — the inner loop finishes completely on each pass of the outer one.

Nested Loop: A loop written inside the body of another loop.
Outer Loop: The loop that contains another loop inside it.
Inner Loop: The loop nested inside another — it completes fully for every pass of the outer loop.