Here is a clear, simple, and exam-oriented explanation of Decision Making Statements in Python, suitable for BCA/MCA/B.Tech students.

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Decision Making Statements in Python

Decision-making statements allow a program to choose different actions based on certain conditions.

In Python, decisions are made using conditional statements, mainly:

1. if
2. if-else
3. if-elif-else
4. Nested if
5. Short-hand if and if-else

These statements allow Python programs to behave differently depending on inputs or logical conditions.

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1. The if Statement

Used to check a condition.
If the condition is True, the block of code inside if runs.

Syntax:

if condition:
    statement(s)

Example:

age = 20
if age >= 18:
    print("You are an adult.")

Output:

You are an adult.

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2. The if-else Statement

Used when you need two possible outcomes.

Syntax:

if condition:
    statement(s)
else:
    statement(s)

Example:

marks = 40
if marks >= 50:
    print("Pass")
else:
    print("Fail")

Output:

Fail

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3. The if-elif-else Statement

Used when checking multiple conditions.

Syntax:

if condition1:
    statement 1
elif condition2:
    statement 2
elif condition3:
    statement 3
else:
    default statement

Example:

marks = 75

if marks >= 90:
    print("Grade A")
elif marks >= 75:
    print("Grade B")
elif marks >= 50:
    print("Grade C")
else:
    print("Fail")

Output:

Grade B

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4. Nested if Statement

An if inside another if.
Used for multiple-level checking.

Example:

age = 25
citizen = True

if age >= 18:
    if citizen:
        print("Eligible to vote")
    else:
        print("Not a citizen")
else:
    print("Underage")

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5. Short-Hand if Statement

If the body contains only one statement, you can write it on one line.

Example:

x = 10
if x > 5: print("Greater")

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6. Short-Hand if-else (Ternary Operator)

Single-line version of if-else.

Syntax:

value_if_true if condition else value_if_false

Example:

age = 17
status = "Adult" if age >= 18 else "Minor"
print(status)

Output:

Minor

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7. Using Logical Operators in Decision Making

Combine multiple conditions using:

• and
• or
• not

Example:

age = 20
has_id = True

if age >= 18 and has_id:
    print("Entry allowed")

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8. Using Membership and Identity Checks

Example using in:

fruits = ["apple", "banana"]
if "apple" in fruits:
    print("Apple found")

Example using is:

x = None
if x is None:
    print("Value is None")

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9. Indentation (Important for Exams)

Python uses indentation instead of braces {}.
Indentation defines block structure.

Wrong (no indentation):

if x > 5:
print("Hello")

Correct:

if x > 5:
    print("Hello")

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10. Example Program: Odd or Even

num = int(input("Enter number: "))

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

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11. Example Program: Largest of Three Numbers

a = 10
b = 25
c = 15

if a > b and a > c:
    print("a is largest")
elif b > a and b > c:
    print("b is largest")
else:
    print("c is largest")

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Summary

Statement	Use
if	Single condition
if-else	Two outcomes
if-elif-else	Multiple conditions
Nested if	Condition inside condition
Shorthand if	One-line statement
Ternary	Inline if-else

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