True, False, and Comparisons

Core path: 30 minutes

How does Python turn data into a decision?

Week 3 gave the program values. Week 4 asks questions about those values.

A decision starts with an expression that can be evaluated as True or False.

A Boolean is a value

robot_online = True
game_over = False

True and False are Boolean values. They are not the strings "True" and "False".

Most of the time, you will not type Boolean values directly. Python will produce them by evaluating a comparison.

battery = 18
print(battery <= 20)

Python does not read that as English. It evaluates the left value, the operator, and the right value and produces one Boolean result.

battery → 18
18 <= 20
    ↓
True

That Boolean can later control a branch.

Translate the operator into a question

Use comparisons as questions:

This is better than memorizing symbols in isolation because requirements usually arrive in words first.

Words such as at least, no more than, below, and greater than hide exact boundary rules.

Assignment and comparison are different operations

score = 100

changes program state by assigning a value.

score == 100

evaluates a question and produces True or False.

One equals sign and two equals signs are not alternate spellings.

Try reading them aloud:

score = 100   → assign 100 to score
score == 100  → is score equal to 100?

That difference becomes much easier to remember when you attach a job to each operator.

Boundary language matters

Suppose the requirement says:

A battery is low at 20 percent or below.

Then:

battery <= 20

matches the requirement.

This does not:

battery < 20

The second expression excludes exactly 20.

Test the boundary pair:

19 → True
20 → True
21 → False

Use the runtime to make that one-character policy change visible:

Run the code to see output.

One character in the operator can change the policy of the program.

Comparisons work with strings too

username = "neo"

print(username == "neo")  # True
print(username == "Neo")  # False

Python strings are case-sensitive by default. Those values contain different characters.

If your requirement says capitalization should not matter, you need to normalize or otherwise define that behavior deliberately. Python will not infer the policy.

Predict the Boolean evidence

score = 75

print(score > 50)
print(score == 75)
print(score != 75)
print(score <= 100)

Before running, trace one value through four questions:

75 > 50    → True
75 == 75   → True
75 != 75   → False
75 <= 100  → True

Then run it.

If one prediction was wrong, identify whether you misunderstood the value, the operator, or the boundary.

A Boolean expression is evidence, not action

This line:

score >= 70

can evaluate to True, but by itself it does not print anything, grant access, or move a robot.

It produces information.

Lesson 2 uses that information to choose an execution path.

That separation is important:

comparison → Boolean result
branch     → action chosen because of that result

Boolean Detective

Given:

age = 15
score = 82
username = "nova"
is_admin = False

Predict:

age >= 13
score > 90
username == "nova"
username == "Nova"
is_admin == True
score != 82

For each expression, record:

left value:
operator:
right value:
result:

For is_admin == True, ask whether the comparison is even necessary. A Boolean variable can often be used directly later:

if is_admin:
    ...

We will use that in Lesson 3.