Lesson 7 — Decision Making

Conditional Statements

Python's conditionals are minimal and readable. elif not else if, no parentheses required around conditions, and match/case (Python 3.10+) for pattern matching.

PYTHON — if/elif/else 
mark = 74

if mark >= 80:
    print("Distinction")
elif mark >= 70:
    print("Merit — Upper")
elif mark >= 60:
    print("Merit")
elif mark >= 50:
    print("Pass")
else:
    print("Not yet competent")

# No parentheses needed around the condition (unlike Java/C#)
# elif not "else if"

Ternary Expression

PYTHON — Ternary 
# Python ternary: value_if_true if condition else value_if_false
result = "Pass" if mark >= 50 else "Fail"
print(result)

# Nested ternary — avoid for readability:
grade = ("Distinction" if mark >= 80
         else "Merit" if mark >= 60
         else "Pass" if mark >= 50
         else "Fail")
print(grade)

match/case (Python 3.10+)

Python's structural pattern matching is more powerful than a simple switch — it matches structures, types, and values simultaneously.

PYTHON — match/case 
day = "Wednesday"

match day:
    case "Monday":
        print("Java fundamentals — 09:00 to 13:00")
    case "Tuesday":
        print("Data types and operators")
    case "Wednesday":
        print("Career development and CV writing")
    case "Thursday":
        print("Project work and peer review")
    case "Friday":
        print("Presentations and feedback")
    case _:  # default
        print("Self-study recommended")

# Match with guards:
match mark:
    case n if n >= 80:
        print(f"{n}% — Distinction")
    case n if n >= 50:
        print(f"{n}% — Pass")
    case _:
        print("Not yet competent")

Practice Task

Your Turn

Write a program with a hardcoded mark and a boolean for whether the learner submitted on time. Use if/elif/else to assign a grade label. Use the ternary operator for a one-line pass/fail string. Add a nested if for late submission with a penalty message. Use match/case for the day-of-week schedule.

Common Mistakes

  • Python uses elif, not else if (two words causes SyntaxError).
  • Forgetting the colon after if, elif, else.
  • Wrong indentation in the elif chain.
  • match/case requires Python 3.10+ — check with python --version.

Professional Tip

The ordering of conditions in an if/elif chain matters critically. Always put the most restrictive condition first. A mark of 90 hitting elif mark >= 50 first would be wrongly labelled Pass.

Mini Quiz

Python's keyword for additional conditions after if is?