PART 1 • LEVEL 04

🔀 Decision Making

Teach your Python programs to inspect conditions, choose the correct path and respond clearly to different situations.

⏱ 85–100 minutes📚 8 concepts💻 5 programs🧠 6-question quiz

result.pyPython 3

score = 72

if score >= 75:
    grade = "Distinction"
elif score >= 60:
    grade = "Good"
else:
    grade = "Keep Practising"

print(grade)

OUTPUTGood

LEARNING OUTCOMES

By the End of This Level

You will be able to design readable and complete decision paths.

Write if, if...else and if...elif...else statements.

Combine comparisons into meaningful conditions.

Use nesting and conditional expressions carefully.

Choose between conditional chains and match...case.

CHOOSE A PATH

Conditions and Control Flow

A condition is an expression that Python treats as true or false. Control flow decides which statement runs next.

Python evaluates the condition after if. When it is True, the indented block runs. When it is False, Python skips that block and continues with the next available path.

Decision

A point where program execution follows one path and skips another according to a condition.

1Read DataGet current values

→

2Test ConditionTrue or False

→

3Choose BlockRun one path

→

4ContinueResume the program

ONE-WAY DECISION

The `if` Statement

Use a simple if when an action is needed only for the true case.

EXAMPLE 1

Free Delivery Check

order_total = 850

if order_total >= 500:
    print("Free delivery unlocked")

print("Order checked")

OUTPUT

Free delivery unlocked
Order checked

Indentation creates the block

The colon begins the decision block. Every statement controlled by that if must use consistent indentation—normally four spaces.

TWO-WAY DECISION

`if...else`

Use else when exactly one of two mutually exclusive actions must run.

EXAMPLE 2

Even or Odd

number = 27

if number % 2 == 0:
    print("Even")
else:
    print("Odd")

OUTPUT

Odd

TRUE PATH

if balance >= price:
    print("Purchase approved")

Runs only when the condition is true.

FALSE PATH

else:
    print("Insufficient balance")

Runs only when the preceding condition is false.

MULTI-WAY DECISION

`if...elif...else`

An elif chain checks conditions from top to bottom and runs only the first matching block.

EXAMPLE 3

Performance Band

score = 86

if score >= 90:
    band = "Excellent"
elif score >= 75:
    band = "Very Good"
elif score >= 60:
    band = "Good"
else:
    band = "Needs Improvement"

print(band)

OUTPUT

Very Good

Order matters

Place the most restrictive or highest range first. If score >= 60 appeared before score >= 90, a score of 95 would stop at the wrong branch.

DECISIONS INSIDE DECISIONS

Nested and Combined Conditions

COMBINED

Use logical operators

Best when all requirements form one clear rule.

if age >= 18 and score >= 60:
    print("Eligible")

NESTED

Use an inner decision

Useful when the second test matters only after the first succeeds.

if account_active:
    if balance >= price:
        print("Approved")

READABILITY

Name complex conditions

A descriptive Boolean variable explains the rule.

can_apply = age >= 18 and score >= 60
if can_apply:
    print("Eligible")

ONE-LINE CHOICE

Conditional Expression

A conditional expression chooses between two values. Keep it for short, simple assignments.

EXAMPLE 4

Access Label

age = 20
label = "Adult" if age >= 18 else "Minor"
print(label)

OUTPUT

Adult

Read it in this order

true_value if condition else false_value. Use a normal statement when the branches perform several actions or the one-line form becomes difficult to scan.

PATTERN SELECTION

`match...case`

Python 3.10+ can match one value or pattern against several cases. The underscore _ acts as the default case.

EXAMPLE 5

Menu Command

command = "save"

match command:
    case "open":
        print("Opening file")
    case "save":
        print("Saving file")
    case "quit":
        print("Closing program")
    case _:
        print("Unknown command")

OUTPUT

Saving file

Situation	Prefer	Reason
Ranges such as marks or age	`if...elif`	Comparisons express ranges clearly.
Exact commands or structured patterns	`match...case`	Cases keep discrete choices readable.
Only two returned values	Conditional expression	Concise when the rule is simple.

DEBUGGING CORNER

Common Decision-Making Mistakes

Comparison

if score = 50:

Use == to compare; = is assignment.

Indentation

print("Approved")

Indent every controlled statement consistently under its decision header.

Ordering

if score >= 40

Check higher thresholds before lower ones in an ordered elif chain.

Coverage

if number > 0

Include zero and negative paths when the problem requires all possibilities.

Debug decisions:1. List every possible path2. Test boundary values3. Check branch order4. Verify indentation5. Confirm exactly one result

QUICK REVISION

📌 Decision Making — Quick Revision

Review these rules before attempting the quiz and programming problems.

A condition is interpreted as True or False.

if runs its block only for a true condition.

else handles the remaining false path.

elif adds ordered alternatives.

Only the first matching block in an elif chain runs.

Four consistent spaces are the standard indentation.

Use and, or and not to combine rules.

Boundary values reveal missing or overlapping ranges.

A conditional expression chooses between two values.

match...case suits clear discrete patterns.

KNOWLEDGE CHECK

Level 4 Quick Quiz

Select one answer for every question, then check your score.

6 Questions

1Which symbol finishes an if header? Semicolon Colon Comma Period

2What does an elif chain execute? Every true block Only the final block The first matching block No block

3What is printed for number = 0 and if number:? The block is skipped The block runs None Syntax error

4Which condition checks whether age is from 18 through 60 inclusive?age > 18 or age < 6018 > age > 60age == 18 and 6018 <= age <= 60

5Which is a valid conditional expression?if age >= 18 then "Adult""Adult" if age >= 18 else "Minor"age ? "Adult" : "Minor"if(age) "Adult"

6Which match pattern is commonly used as the default?*else_default

PRACTICE

🎯 5 Programming Problems — Decision Making

Solve every problem in the CodeBhavya pattern: understand the rule, inspect the sample, try the editor, run, check, then compare with the official program.

📈 Decision-Making Practice Progress

Solved0 / 5

Completed with Solution0

Total Score0 / 500

Completion0%

A problem counts as Solved when its output passes before the official solution is opened.

1. Number Sign Classifier

Read an integer and display whether it is positive, negative or zero.

Sample input: 0Expected output: Zero

💡 Test positive first, negative second, and let else handle zero.

Official Python Program

number = int(input())
if number > 0:
    print("Positive")
elif number < 0:
    print("Negative")
else:
    print("Zero")

2. Even or Odd

Read an integer and display whether it is even or odd.

Sample input: 27Expected output: Odd

Official Python Program

number = int(input())
if number % 2 == 0:
    print("Even")
else:
    print("Odd")

3. Grade Classifier

Assign A for 90+, B for 75–89, C for 60–74, D for 40–59 and F otherwise.

Sample input: 86Expected output: Grade = B

Official Python Program

mark = int(input())
if mark >= 90:
    grade = "A"
elif mark >= 75:
    grade = "B"
elif mark >= 60:
    grade = "C"
elif mark >= 40:
    grade = "D"
else:
    grade = "F"
print("Grade =", grade)

4. Largest of Three

Read three integers and display the largest value.

Sample input: 18, 42, 31Expected output: Largest = 42

Official Python Program

a = int(input())
b = int(input())
c = int(input())
if a >= b and a >= c:
    largest = a
elif b >= a and b >= c:
    largest = b
else:
    largest = c
print("Largest =", largest)

5. Placement Eligibility

A learner is eligible when age is at least 18, percentage is at least 60 and backlogs are zero.

Sample input: 20, 72, 0Expected output: Eligible

💡 All three comparisons must be true, so join them with and.

Official Python Program

age = int(input())
percentage = int(input())
backlogs = int(input())
if age >= 18 and percentage >= 60 and backlogs == 0:
    print("Eligible")
else:
    print("Not Eligible")

KEY TAKEAWAY

🎯 Make Every Path Complete

1List

Identify every possible outcome.

→

2Order

Place conditions from specific to general.

→

3Choose

Run exactly the intended branch.

→

4Test

Verify boundaries and exceptions.

Reliable decisions come from complete paths, correct ordering and boundary tests—not from adding more conditions than the problem needs.

INTERACTIVE LEARNING

🎬 Decision Making — Visual Flow

Watch Python test score = 72, skip a false branch and select the first true branch.

PROGRAM TRACING

🔎 Program Tracing — Eligibility Decision

Move through one statement at a time and observe the condition, chosen branch, variables and output.

INTERVIEW PREPARATION

🎤 Decision Making — Interview Questions

Answer aloud before opening each explanation.

What is the difference between independent if statements and an elif chain?

Independent if statements are all tested and several blocks may run. An elif chain stops after its first matching block.

Why does indentation matter in Python decisions?

Indentation defines which statements belong to each branch. Incorrect indentation can change control flow or raise an IndentationError.

Why should higher thresholds appear first in a grade chain?

When is nesting preferable to one combined condition?

What are truthy and falsy values?

Truthy values behave like True in a condition. Values such as 0, None and empty collections are falsy.

When should match...case be considered?

Consider it for clear exact-value or structural pattern selection. Range comparisons are usually more readable with if...elif.

EXTRA TIPS

💡 Decision Making — Extra Tips

01
Test the values immediately below, at and above every boundary.
02
Use descriptive Boolean names such as is_eligible and has_access.
03
Keep decision blocks short; move repeated work after the chain.
04
Prefer a flat elif chain when deep nesting reduces readability.
05
Use in for a small group of accepted exact values.
06
Add an else only when a genuine default path exists.

EXTRA PRACTICE

✍️ Decision Making — Extra Practice Questions

Read a year and decide whether it is a leap year.
Read three side lengths and decide whether they can form a valid triangle.
Classify a character as a vowel, consonant, digit or other symbol.
Calculate an electricity-bill category from a given unit range.
Display the smallest of four integers without using min().
Check whether a date's month number belongs to a 30-day, 31-day or February group.
Create a login decision using username, password and active-account status.
Rewrite a two-branch assignment as a conditional expression.
Build a menu with match...case for add, view, edit and quit commands.
Trace a deliberately misordered grade chain, explain the bug and correct it.

LEVEL 4 CHECKPOINT

Decision Making Complete

When you can design complete branches, handle boundary values and solve all five programs without help, mark this level complete and continue.

Continue to Level 5 →

🔀 Decision Making

By the End of This Level

Conditions and Control Flow

The if Statement

Free Delivery Check

if...else

Even or Odd

if...elif...else

Performance Band

Nested and Combined Conditions

Use logical operators

Use an inner decision

Name complex conditions

Conditional Expression

Access Label

match...case

Menu Command

Common Decision-Making Mistakes

📌 Decision Making — Quick Revision

Level 4 Quick Quiz

🎯 5 Programming Problems — Decision Making

Python Code Editor

Program Output

Test Case

Python Code Editor

Program Output

Test Case

Python Code Editor

Program Output

Test Case

Python Code Editor

Program Output

Test Case

Python Code Editor

Program Output

Test Case

🎯 Make Every Path Complete

🎬 Decision Making — Visual Flow

🔀 How Python Chooses a Branch

1. Read the Current Value

🔎 Program Tracing — Eligibility Decision

🎤 Decision Making — Interview Questions

💡 Decision Making — Extra Tips

✍️ Decision Making — Extra Practice Questions

Decision Making Complete

The `if` Statement

`if...else`

`if...elif...else`

`match...case`