Variables, values, and expressions

Learning objectives

• Distinguish a variable name from its value.
• Use strings, integers, floats, and booleans.
• Combine values with arithmetic and f-strings.

Example

student = "Mina"          # string
projects_completed = 3    # integer
average_score = 91.5      # float
is_ready = True           # boolean

print(f"{student} completed {projects_completed} projects.")
print(f"Average score: {average_score}%")
print(f"Ready for the next lesson: {is_ready}")

The value on the right is assigned to the name on the left. Python determines the type from the value. Use type(value) while learning to inspect a value.

Expressions

robot_distance = 12
additional_distance = 5
total_distance = robot_distance + additional_distance
remaining_distance = 30 - total_distance

print(total_distance, remaining_distance)

Use parentheses when they make the order of operations clearer. Keep units in variable names when confusion is possible, such as distance_cm and distance_m.

Practice

1. Create variables for a robot’s battery percentage and name.
2. Calculate the battery percentage after using 18 points.
3. Print a sentence describing the result.
4. Inspect the types of all three values.

Common mistakes

• score = "91" is text, not a number.
• Score and score are different names.
• A name should describe what it stores.
• Do not overwrite a useful value unless the change is intentional.

Checkpoint

Explain the difference between 5, 5.0, and "5". Then predict the output before running a short example.