Python Conditional Statements

A conditional statement allows a Python program to make decisions based on whether a condition is True or False.

In real programs, we constantly need to make decisions:

If the user is logged in → show the dashboard.
If the age is 18 or above → allow registration.
If marks are above 40 → student passes.
If the password is incorrect → reject login.
If the price is above a certain amount → apply a discount.

Python mainly provides:

if
elif
else

Conditional statements work closely with comparison operators and logical operators.

1. The `if` Statement

The if statement executes a block of code only when its condition is True.

Syntax

if condition:
    # code to execute

Example:

age = 25

if age >= 18:
    print("You are eligible.")

Output:

You are eligible.

Because:

age >= 18

is True.

2. Understanding the Colon `:`

Python uses a colon after the condition:

if age >= 18:

The colon tells Python that a new block of code is beginning.

For example:

if age >= 18:
    print("Eligible")

The code after the colon must belong to the if block.

3. Indentation

Python uses indentation to define blocks of code.

Correct:

age = 25

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

Both print() statements belong to the if block.

Incorrect:

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

This causes an IndentationError.

Recommended style

Use 4 spaces for indentation.

if condition:
    statement

4. Condition Must Produce a Boolean Result

A condition normally evaluates to:

True

or:

False

Example:

age = 25

print(age >= 18)

Output:

True

We can use that condition directly:

if age >= 18:
    print("Adult")

5. Using `==` in Conditions

The equality operator == is commonly used in conditions.

name = "Raj"

if name == "Raj":
    print("Welcome Raj")

Output:

Welcome Raj

Remember:

means assignment.

==

means comparison.

6. Using Comparison Operators

All comparison operators can be used inside conditions.

age = 25

if age > 18:
    print("Age is greater than 18")

if age == 25:
    print("Age is 25")

if age != 30:
    print("Age is not 30")

Common operators:

==
!=
>
<
>=
<=

7. The `else` Statement

else executes when the if condition is False.

Syntax

if condition:
    # if condition is True else:
    # if condition is False

Example:

age = 16

if age >= 18:
    print("You can vote.")
else:
    print("You cannot vote yet.")

Output:

You cannot vote yet.

8. `if` + `else` Flow

Consider:

age = 20

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

The flow is:

          age >= 18?
          /       \
       True       False
        /           \
     Adult         Minor

Only one branch executes.

9. The `elif` Statement

elif means:

else if

It allows us to check another condition when the previous condition was false.

Example:

marks = 75

if marks >= 80:
    print("A+")
elif marks >= 70:
    print("A")
else:
    print("Below A")

Output:

10. Multiple `elif` Conditions

We can have multiple elif statements.

marks = 65

if marks >= 80:
    print("A+")
elif marks >= 70:
    print("A")
elif marks >= 60:
    print("B+")
elif marks >= 50:
    print("B")
else:
    print("Fail")

Output:

B+

Python checks the conditions from top to bottom.

11. Important: Only the First Matching Branch Executes

Consider:

marks = 85

if marks >= 50:
    print("Pass")
elif marks >= 80:
    print("Excellent")

Output:

Pass

Why didn't "Excellent" print?

Because the first condition:

marks >= 50

is already True.

Python executes that block and skips the remaining elif conditions.

Therefore, when using ranges, put more specific/highest conditions first.

Correct:

if marks >= 80:
    print("Excellent")
elif marks >= 50:
    print("Pass")
else:
    print("Fail")

12. Multiple Conditions Using `and`

The and operator requires both conditions to be True.

Example:

age = 25 has_id = True

if age >= 18 and has_id:
    print("Access granted")
else:
    print("Access denied")

Output:

Access granted

Both conditions must be satisfied.

13. Multiple Conditions Using `or`

or requires at least one condition to be True.

day = "Sunday"

if day == "Saturday" or day == "Sunday":
    print("Weekend")
else:
    print("Working day")

Output:

Weekend

14. Using `not`

not reverses a Boolean result.

logged_in = False

if not logged_in:
    print("Please login first.")

Output:

Please login first.

15. Combining `and`, `or`, and `not`

Conditions can be combined.

age = 25 has_id = True has_ticket = True

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

All three conditions must be true.

16. Conditions with Strings

Conditional statements can compare strings.

username = "admin"

if username == "admin":
    print("Administrator")
else:
    print("Regular User")

17. Case-Sensitive String Comparison

Python string comparisons are case-sensitive.

username = "Admin"

if username == "admin":
    print("Correct")
else:
    print("Different username")

Output:

Different username

To make the comparison case-insensitive:

username = "Admin"

if username.lower() == "admin":
    print("Correct username")

18. Conditions with User Input

A very common pattern is:

name = input("Enter your name: ")

if name == "Raj":
    print("Welcome Raj")
else:
    print("Welcome Guest")

User input is stored in the variable and then evaluated.

19. Numeric User Input

Remember that input() returns a string.

Therefore:

age = input("Enter your age: ")

should normally be converted before numeric comparison:

age = int(input("Enter your age: "))

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

20. Practical Example : Voting Eligibility

age = int(input("Enter your age: "))

if age >= 18:
    print("You are eligible to vote.")
else:
    print("You are not eligible to vote.")

This is a simple real-world decision-making program.

21. Practical Example : Even or Odd

The modulus operator can be combined with conditions.

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

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

If:

number = 12

then:

12 % 2 = 0

so the number is even.

22. Practical Example : Positive, Negative, or Zero

We can use multiple conditions.

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

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

Possible results:

10 → Positive
-5 → Negative
0 → Zero

23. Practical Example : Student Grade

marks = float(input("Enter your marks: "))

if marks >= 80:
    print("Grade: A+")
elif marks >= 70:
    print("Grade: A")
elif marks >= 60:
    print("Grade: B+")
elif marks >= 50:
    print("Grade: B")
elif marks >= 40:
    print("Grade: C")
else:
    print("Grade: Fail")

This is a practical example of using multiple elif conditions.

24. Practical Example : Pass or Fail

Suppose a student must score at least 40 in every subject.

python_marks = 65 database_marks = 55 web_marks = 70

if python_marks >= 40 and database_marks >= 40 and web_marks >= 40:
    print("Pass")
else:
    print("Fail")

Here, all three conditions must be true.

25. Nested `if`

An if statement inside another if statement is called a nested if.

Example:

age = 25 has_id = True

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

The second condition is checked only when the first condition is true.

26. Nested `if` with `else`

age = 20 has_id = False

if age >= 18:
    if has_id:
        print("Entry allowed")
    else:
        print("ID required")
else:
    print("You are underage")

Output:

ID required

27. Nested Conditions in Real Programs

Nested conditions can represent multiple levels of decisions.

For example:

username = input("Username: ")
password = input("Password: ")

if username == "admin":
    if password == "python123":
        print("Login successful")
    else:
        print("Incorrect password")
else:
    print("Unknown username")

28. Avoid Unnecessary Nesting

Sometimes nested conditions can be simplified.

Instead of:

if age >= 18:
    if has_id:
        print("Allowed")

we can write:

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

The second version is often easier to read.

29. `if` with Membership Operators

The in operator works well with conditions.

courses = ["Python", "Django", "MERN"]

course = input("Enter course: ")

if course in courses:
    print("Course available")
else:
    print("Course not available")

30. `if` with Dictionaries

Remember that in checks dictionary keys.

student = {
    "name": "Raj",
    "age": 25,
    "course": "Python"
}

if "course" in student:
    print("Course information is available")

31. Checking Dictionary Values

student = {
    "name": "Raj",
    "age": 25,
    "course": "Python"
}

if "Python" in student.values():
    print("Student is learning Python")

32. Conditions with Lists

A list can also be used in a condition.

students = ["Raj", "John", "Sita"]

name = input("Enter your name: ")

if name in students:
    print("Student found")
else:
    print("Student not found")

33. Truthy and Falsy Values

Python does not always require an explicit comparison.

For example:

name = "Raj"

if name:
    print("Name is available")

Because "Raj" is a non-empty string, it is considered truthy.

An empty string is considered falsy:

name = ""

if name:
    print("Name is available")
else:
    print("Name is empty")

Output:

Name is empty

34. Common Falsy Values

These values are generally considered false in conditions:

False None 0 0.0 ""
[]
()
{}
set()

Example:

items = []

if items:
    print("Items are available")
else:
    print("No items found")

Output:

No items found

35. Using `bool()` to Understand Conditions

You can see how Python evaluates values:

print(bool(0))
print(bool(10))
print(bool(""))
print(bool("Python"))
print(bool([]))
print(bool([1, 2]))

Output:

False
True
False
True
False
True

This becomes useful when understanding conditions.

36. Conditional Expression : Ternary Operator

Python allows a simple if-else decision to be written in one line.

Example:

age = 20

result = "Adult" if age >= 18 else "Minor"

print(result)

Output:

Adult

The structure is:

value_if_true if condition else value_if_false

37. Ternary Example

number = 10

result = "Even" if number % 2 == 0 else "Odd"

print(result)

Output:

Even

Ternary expressions are useful for simple decisions, but regular if-else is often easier to read when the logic becomes complicated.

38. Nested Ternary : Use Carefully

Python technically allows:

marks = 75

grade = "A+" if marks >= 80 else "A" if marks >= 70 else "B"

print(grade)

This works, but it can become difficult to read.

For beginners, prefer:

if marks >= 80:
    grade = "A+" elif marks >= 70:
    grade = "A" else:
    grade = "B"

Readable code is usually better than clever code.

39. Using `pass`

Sometimes you want to create a condition but don't want to write its implementation yet.

Python provides:

pass

Example:

age = 25

if age >= 18:
    pass else:
    print("Minor")

pass does nothing.

It acts as a placeholder.

40. Common Mistake : Using `=` Instead of `==`

Incorrect:

age = 18

if age = 18:
    print("Correct")

This produces a syntax error.

Correct:

if age == 18:
    print("Correct")

Remember:

=   → assignment
==  → comparison

41. Common Mistake : Forgetting the Colon

Incorrect:

if age >= 18
    print("Adult")

Correct:

if age >= 18:
    print("Adult")

42. Common Mistake : Incorrect Indentation

Incorrect:

if age >= 18:
print("Adult")

Correct:

if age >= 18:
    print("Adult")

43. Common Mistake : Comparing Input Without Conversion

Potential problem:

age = input("Enter age: ")

if age >= 18:
    print("Adult")

age is a string, so this comparison is invalid.

Correct:

age = int(input("Enter age: "))

if age >= 18:
    print("Adult")

44. Common Mistake : Wrong Condition Order

Avoid:

marks = 85

if marks >= 40:
    print("Pass")
elif marks >= 80:
    print("Excellent")

The elif will never be reached for marks of 80 or more.

Better:

if marks >= 80:
    print("Excellent")
elif marks >= 40:
    print("Pass")
else:
    print("Fail")

45. Practical Example : Login System

username = input("Enter username: ")
password = input("Enter password: ")

if username == "admin" and password == "python123":
    print("Login successful")
else:
    print("Invalid username or password")

This combines:

input()
String comparison
and
if
else

46. Practical Example : Discount System

amount = float(input("Enter purchase amount: "))

if amount >= 10000:
    discount = 20 elif amount >= 5000:
    discount = 10 elif amount >= 2000:
    discount = 5 else:
    discount = 0

discount_amount = amount * discount / 100 final_amount = amount - discount_amount

print("Discount:", discount, "%")
print("Discount Amount:", discount_amount)
print("Final Amount:", final_amount)

This is a good example of a real business rule implemented using conditional statements.

47. Practical Example : Course Eligibility

age = int(input("Enter your age: "))
education = input("Enter your education level: ")

if age >= 18 and education == "Bachelor":
    print("Eligible for the advanced program")
elif age >= 18:
    print("Eligible for the basic program")
else:
    print("Not eligible")

48. Practical Example : ATM Withdrawal

balance = 10000

amount = float(input("Enter withdrawal amount: "))

if amount <= 0:
    print("Invalid amount")
elif amount > balance:
    print("Insufficient balance")
else:
    balance = balance - amount
    print("Withdrawal successful")
    print("Remaining balance:", balance)

This demonstrates how multiple conditions can protect a program from invalid input.

49. Practical Example : Temperature

temperature = float(input("Enter temperature: "))

if temperature >= 35:
    print("Very Hot")
elif temperature >= 25:
    print("Warm")
elif temperature >= 15:
    print("Moderate")
else:
    print("Cold")

50. Copy Code

The following section contains the complete copy-ready code for this lesson.

# ========================================== # Python Conditional Statements # ==========================================


# ------------------------------------------ # 1. Basic if statement # ------------------------------------------

age = 25

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


# ------------------------------------------ # 2. if with comparison # ------------------------------------------

number = 10

if number == 10:
    print("Number is 10")


# ------------------------------------------ # 3. if and else # ------------------------------------------

age = 16

if age >= 18:
    print("You can vote.")
else:
    print("You cannot vote yet.")


# ------------------------------------------ # 4. if, elif and else # ------------------------------------------

marks = 75

if marks >= 80:
    print("A+")
elif marks >= 70:
    print("A")
elif marks >= 60:
    print("B+")
elif marks >= 50:
    print("B")
elif marks >= 40:
    print("C")
else:
    print("Fail")


# ------------------------------------------ # 5. Multiple conditions using and # ------------------------------------------

age = 25 has_id = True

if age >= 18 and has_id:
    print("Access granted")
else:
    print("Access denied")


# ------------------------------------------ # 6. Multiple conditions using or # ------------------------------------------

day = "Sunday"

if day == "Saturday" or day == "Sunday":
    print("Weekend")
else:
    print("Working day")


# ------------------------------------------ # 7. Using not # ------------------------------------------

logged_in = False

if not logged_in:
    print("Please login first.")


# ------------------------------------------ # 8. String comparison # ------------------------------------------

username = "admin"

if username == "admin":
    print("Administrator")
else:
    print("Regular User")


# ------------------------------------------ # 9. Case-insensitive comparison # ------------------------------------------

username = "Admin"

if username.lower() == "admin":
    print("Correct username")
else:
    print("Incorrect username")


# ------------------------------------------ # 10. User input # ------------------------------------------

name = input("Enter your name: ")

if name == "Raj":
    print("Welcome Raj")
else:
    print("Welcome Guest")


# ------------------------------------------ # 11. Numeric user input # ------------------------------------------

age = int(input("Enter your age: "))

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


# ------------------------------------------ # 12. Even or odd # ------------------------------------------

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

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


# ------------------------------------------ # 13. Positive, negative or zero # ------------------------------------------

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

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


# ------------------------------------------ # 14. Nested if # ------------------------------------------

age = 25 has_id = True

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


# ------------------------------------------ # 15. Nested if with else # ------------------------------------------

age = 20 has_id = False

if age >= 18:
    if has_id:
        print("Entry allowed")
    else:
        print("ID required")
else:
    print("You are underage")


# ------------------------------------------ # 16. Membership operator # ------------------------------------------

courses = ["Python", "Django", "MERN"]

course = "Python"

if course in courses:
    print("Course available")
else:
    print("Course not available")


# ------------------------------------------ # 17. Dictionary condition # ------------------------------------------

student = {
    "name": "Raj",
    "age": 25,
    "course": "Python"
}

if "course" in student:
    print("Course information is available")

if "Python" in student.values():
    print("Student is learning Python")


# ------------------------------------------ # 18. Truthy and falsy values # ------------------------------------------

name = ""

if name:
    print("Name is available")
else:
    print("Name is empty")


# ------------------------------------------ # 19. Ternary / conditional expression # ------------------------------------------

age = 20

result = "Adult" if age >= 18 else "Minor"

print(result)


# ------------------------------------------ # 20. Ternary even/odd # ------------------------------------------

number = 10

result = "Even" if number % 2 == 0 else "Odd"

print(result)


# ------------------------------------------ # 21. pass statement # ------------------------------------------

age = 25

if age >= 18:
    pass else:
    print("Minor")


# ------------------------------------------ # 22. Login system # ------------------------------------------

username = input("Enter username: ")
password = input("Enter password: ")

if username == "admin" and password == "python123":
    print("Login successful")
else:
    print("Invalid username or password")


# ------------------------------------------ # 23. Discount system # ------------------------------------------

amount = float(input("Enter purchase amount: "))

if amount >= 10000:
    discount = 20 elif amount >= 5000:
    discount = 10 elif amount >= 2000:
    discount = 5 else:
    discount = 0

discount_amount = amount * discount / 100 final_amount = amount - discount_amount

print("Discount:", discount, "%")
print("Discount Amount:", discount_amount)
print("Final Amount:", final_amount)


# ------------------------------------------ # 24. ATM withdrawal # ------------------------------------------

balance = 10000

amount = float(input("Enter withdrawal amount: "))

if amount <= 0:
    print("Invalid amount")
elif amount > balance:
    print("Insufficient balance")
else:
    balance = balance - amount
    print("Withdrawal successful")
    print("Remaining balance:", balance)

51. Practice Exercise 1 : Age Category

Ask the user for their age.

Display:

0–12     → Child
13–19    → Teenager
20–59    → Adult
60+      → Senior Citizen

Use if, elif, and else.

52. Practice Exercise 2 : Number Checker

Ask the user for a number.

Determine whether it is:

Positive
Negative
Zero

Then additionally determine whether a positive number is:

Even
Odd

53. Practice Exercise 3 : Login System

Create a login program with:

correct_username = "admin" correct_password = "python123"

Ask the user for username and password.

Display:

Login successful

or:

Invalid username or password

54. Practice Exercise 4 : Grade Calculator

Ask for marks and display:

90–100 → A+
80–89  → A
70–79  → B+
60–69  → B
50–59  → C+
40–49  → C
Below 40 → Fail

Also make sure marks are within a valid range of 0–100.

55. Practice Exercise 5 : Simple Calculator

Ask the user for:

First number
Second number
Operator

For example:

Enter first number: 20
Enter second number: 5
Enter operator: *

Display:

Result: 100

Support:

+
-
*
/
%

This is an excellent exercise for combining:

input()
Type conversion
if
elif
Arithmetic operators

56. Practice Exercise 6 : Shopping Discount

Create a discount system:

Purchase >= 10000 → 20% discount
Purchase >= 5000  → 10% discount
Purchase >= 2000  → 5% discount
Below 2000        → No discount

Calculate the final amount.

57. Challenge : ATM System

Create a simple ATM program.

Starting balance:

balance = 50000

Ask the user for withdrawal amount.

Rules:

Amount <= 0       → Invalid amount
Amount > balance  → Insufficient balance
Otherwise         → Withdrawal successful

Display the remaining balance after a successful withdrawal.

58. Challenge : Course Admission System

Create a program for SkillMantra course admission.

Ask for:

Age
Education
Programming experience

Example rules:

Age >= 18 AND education == "Bachelor"
    → Eligible for Advanced Program

Age >= 18
    → Eligible for Beginner Program

Age < 18
    → Not eligible

Extend the program with your own rules.

1. The if Statement

Syntax

2. Understanding the Colon :

3. Indentation

Recommended style

4. Condition Must Produce a Boolean Result

5. Using == in Conditions

6. Using Comparison Operators

7. The else Statement

Syntax

8. if + else Flow

9. The elif Statement

10. Multiple elif Conditions

11. Important: Only the First Matching Branch Executes

12. Multiple Conditions Using and

13. Multiple Conditions Using or

14. Using not

15. Combining and, or, and not

16. Conditions with Strings

17. Case-Sensitive String Comparison

18. Conditions with User Input

19. Numeric User Input

20. Practical Example : Voting Eligibility

21. Practical Example : Even or Odd

22. Practical Example : Positive, Negative, or Zero

23. Practical Example : Student Grade

24. Practical Example : Pass or Fail

25. Nested if

26. Nested if with else

27. Nested Conditions in Real Programs

28. Avoid Unnecessary Nesting

29. if with Membership Operators

30. if with Dictionaries

31. Checking Dictionary Values

32. Conditions with Lists

33. Truthy and Falsy Values

34. Common Falsy Values

35. Using bool() to Understand Conditions

36. Conditional Expression : Ternary Operator

37. Ternary Example

38. Nested Ternary : Use Carefully

39. Using pass

40. Common Mistake : Using = Instead of ==

41. Common Mistake : Forgetting the Colon

42. Common Mistake : Incorrect Indentation

43. Common Mistake : Comparing Input Without Conversion

44. Common Mistake : Wrong Condition Order

45. Practical Example : Login System

46. Practical Example : Discount System

47. Practical Example : Course Eligibility

48. Practical Example : ATM Withdrawal

49. Practical Example : Temperature

50. Copy Code

51. Practice Exercise 1 : Age Category

52. Practice Exercise 2 : Number Checker

53. Practice Exercise 3 : Login System

54. Practice Exercise 4 : Grade Calculator

55. Practice Exercise 5 : Simple Calculator

56. Practice Exercise 6 : Shopping Discount

57. Challenge : ATM System

58. Challenge : Course Admission System

SkillMantra

1. The `if` Statement

2. Understanding the Colon `:`

5. Using `==` in Conditions

7. The `else` Statement

8. `if` + `else` Flow

9. The `elif` Statement

10. Multiple `elif` Conditions

12. Multiple Conditions Using `and`

13. Multiple Conditions Using `or`

14. Using `not`

15. Combining `and`, `or`, and `not`

25. Nested `if`

26. Nested `if` with `else`

29. `if` with Membership Operators

30. `if` with Dictionaries

35. Using `bool()` to Understand Conditions

39. Using `pass`

40. Common Mistake : Using `=` Instead of `==`