Chapter 6 - Conditional Logic

Chapter 6 is where the program starts making decisions. It introduces conditions, branches, and indentation discipline.

Chapter 6 — Making decisions

EXPLORER · v5 · teaching the console how to react

Where we are now

The console can now ask the user for information and store it correctly.

It knows the mission location, the day number, and the temperature.

At the moment though, it treats every situation the same way.

No matter what the user enters, the output never changes its behaviour.

Programs need to make choices

Real programs do not just display information.

They respond differently depending on what is happening.

For example:

If the system is online, show one message.

If it is offline, show a different one.

In Python, decisions like this are made using if statements.

Decisions depend on true or false

An if statement always checks something that is either True or False.

These true or false values are called booleans.

You met booleans in the last chapter when you stored whether the system was online.

Now we are going to use that value to control what the program does.

How an if statement works

An if statement asks a question.

If the answer is True, Python runs the indented code underneath it.

If the answer is False, that code is skipped.

Indentation matters. Python uses indentation to know which lines belong to the decision.

EXPLORER v5 (run this)

This version of the console reacts to the system state.

Read the comments and watch how the output changes.

"""
EXPLORER v5 — Chapter 6

This version uses if statements to make decisions
based on boolean values.
"""

# =========================
# COLLECT MISSION DETAILS
# =========================

mission_location = input("Enter mission location: ")

mission_day_text = input("Enter mission day (whole number): ")
mission_day = int(mission_day_text)

temperature_text = input("Enter temperature (°C): ")
temperature_c = float(temperature_text)

# =========================
# SYSTEM STATE
# =========================

system_online = True

# =========================
# CONSOLE OUTPUT
# =========================

print("=" * 44)
print("              EXPLORER CONSOLE              ")
print("=" * 44)

print("Location: " + mission_location)
print("Day: " + str(mission_day))
print("Temperature: " + str(temperature_c) + " °C")
print()

print("System status:")

# Decision based on a boolean value
if system_online:
    print("Online: System is operational")
else:
    print("Online: System is offline")

print("=" * 44)

Why indentation matters

Notice that the lines under if and else are indented.

That indentation tells Python which lines belong to each decision.

If the indentation is wrong, Python will either stop with an error or behave in a way you did not expect.

This is one of the most common mistakes beginners make, and it gets easier with practice.

Try this

Change system_online to False.

Run the program again.

Observe which message is printed and which one is skipped.

The program structure stays the same, but the behaviour changes.

Next time

Right now, the console can make simple yes or no decisions.

In the next chapter, we will use comparisons and user input to make more flexible decisions.

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