Literals, Variables, and Constants — Programming Examples

Use these short, runnable examples as demonstration checkpoints. Ask students to predict the output before you run each one.

1. Literals: values written directly in code

whole_number = 7
price = 2.75
initial = "A"
course_name = "Programming in Python"
is_online = True

print(whole_number)
print(price)
print(initial)
print(course_name)
print(is_online)

Teaching point: Quotation marks make text a string; True is Boolean, not the string “True”.

2. Number-looking strings

zip_code = "38843"
pin = "0042"
age = 20

print(zip_code)
print(pin)
print(age + 1)

Teaching point: ZIP codes and PINs are identifiers, not quantities to calculate. Keeping leading zeros requires strings.

3. Variable names communicate purpose

student_name = "Jordan"
current_balance = 125.50
number_of_courses = 4

print(student_name)
print(current_balance)
print(number_of_courses)

Naming reminder: start with a letter or underscore; use descriptive names. student_name is snake case, and studentName is camel case.

4. Variables change; constants should not

MINUTES_PER_HOUR = 60
hours_studied = 2
minutes_studied = hours_studied * MINUTES_PER_HOUR

print(minutes_studied)

hours_studied = 3
minutes_studied = hours_studied * MINUTES_PER_HOUR
print(minutes_studied)

Teaching point: hours_studied changes. MINUTES_PER_HOUR represents a value the program intends to keep fixed.

5. Initialization versus later assignment

score = 0          # initialize
score = 10         # assign a new value
score = score + 5  # use the old value, then store the new value

print(score)

Trace it aloud: score starts as 0, becomes 10, and then becomes 15.

6. Dynamic typing and None

response = None
print(response)

response = 42
print(response)

response = "forty-two"
print(response)

Teaching point: None represents no value yet. Python infers a type from the value assigned, and a variable can later hold a different type.

7. Input is text by default

name = input("What is your name? ")
print("Welcome,", name)

age_text = input("How old are you? ")
print("Next year you will be", int(age_text) + 1)

Teaching point: input() returns a string. Convert it with int() only when the response needs to be used as a whole number.

8. Mini live-coding challenge: study-time calculator

MINUTES_PER_HOUR = 60
student_name = input("Student name: ")
hours = int(input("Hours studied today: "))
minutes = hours * MINUTES_PER_HOUR

print(student_name, "studied for", minutes, "minutes.")

Build sequence:

1. Start with the constant and a hard-coded value for hours.
2. Replace the hard-coded value with input.
3. Add the conversion to int().
4. Add a meaningful output sentence.

Exit-ticket prompts

1. Identify the literal in: campus = “Booneville”
2. Write a snake-case variable name for “number of absences.”
3. Write a constant for the number of days in a week.
4. Trace: total = 3; total = total + 2; print(total).
5. Explain why an area code should usually be stored as text.

Answer key

1. “Booneville”
2. number_of_absences
3. DAYS_PER_WEEK = 7
4. 5
5. It is an identifier and may need leading zeros; it is not normally used in calculations.