Python Elif Statement

The Elif Keyword

The elif keyword is Python's way of saying "if the previous conditions were not true, then try this condition".

The elif keyword allows you to check multiple expressions for True and execute a block of code as soon as one of the conditions evaluates to True.

a = 33
b = 33
if b > a:
  print("b is greater than a")
elif a == b:
  print("a and b are equal")

In this example a is equal to b, so the first condition is not true, but the elif condition is true, so we print to screen that "a and b are equal".

Multiple Elif Statements

You can have as many elif statements as you need. Python will check each condition in order and execute the first one that is true.

score = 75

if score >= 90:
  print("Grade: A")
elif score >= 80:
  print("Grade: B")
elif score >= 70:
  print("Grade: C")
elif score >= 60:
  print("Grade: D")

In this example, the program checks each condition in order. Since score is 75, it prints "Grade: C" (the first condition that evaluates to true).

How Elif Works

When you use elif, Python evaluates the conditions from top to bottom. As soon as it finds a condition that is true, it executes that block and skips all remaining conditions.

age = 25

if age < 13:
  print("You are a child")
elif age < 20:
  print("You are a teenager")
elif age < 65:
  print("You are an adult")
elif age >= 65:
  print("You are a senior")

When to Use Elif

Use elif when you have multiple mutually exclusive conditions to check. This is more efficient than using multiple separate if statements because Python stops checking once it finds a true condition.

day = 3

if day == 1:
  print("Monday")
elif day == 2:
  print("Tuesday")
elif day == 3:
  print("Wednesday")
elif day == 4:
  print("Thursday")
elif day == 5:
  print("Friday")
elif day == 6:
  print("Saturday")
elif day == 7:
  print("Sunday")

Python Else Statement

The Else Keyword

The else keyword catches anything which isn't caught by the preceding conditions.

The else statement is executed when the if condition (and any elif conditions) evaluate to False.

a = 200
b = 33
if b > a:
  print("b is greater than a")
elif a == b:
  print("a and b are equal")
else:
  print("a is greater than b")

In this example a is greater than b, so the first condition is not true, also the elif condition is not true, so we go to the else condition and print to screen that "a is greater than b".

Else Without Elif

You can also have an else without the elif:

a = 200
b = 33
if b > a:
  print("b is greater than a")
else:
  print("b is not greater than a")

This creates a simple two-way choice: if the condition is true, execute one block; otherwise, execute the else block.

How Else Works

The else statement provides a default action when none of the previous conditions are true. Think of it as a "catch-all" for any scenario not covered by your if and elif statements.

number = 7

if number % 2 == 0:
  print("The number is even")
else:
  print("The number is odd")

Complete If-Elif-Else Chain

You can combine if, elif, and else to create a comprehensive decision-making structure.

temperature = 22

if temperature > 30:
  print("It's hot outside!")
elif temperature > 20:
  print("It's warm outside")
elif temperature > 10:
  print("It's cool outside")
else:
  print("It's cold outside!")

Else as Fallback

The else statement acts as a fallback that executes when none of the preceding conditions are true. This makes it useful for error handling, validation, and providing default values.

username = "Emil"

if len(username) > 0:
  print(f"Welcome, {username}!")
else:
  print("Error: Username cannot be empty")

Python Shorthand If

Short Hand If

If you have only one statement to execute, you can put it on the same line as the if statement.

a = 5
b = 2
if a > b: print("a is greater than b")

Short Hand If ... Else

If you have one statement for if and one for else, you can put them on the same line using a conditional expression:

a = 2
b = 330
print("A") if a > b else print("B")

Assign a Value With If ... Else

You can also use a one-line if/else to choose a value and assign it to a variable:

a = 10
b = 20
bigger = a if a > b else b
print("Bigger is", bigger)

The syntax follows this pattern:

variable = value_if_true if condition else value_if_false

Multiple Conditions on One Line

You can chain conditional expressions, but keep it short so it stays readable:

a = 330
b = 330
print("A") if a > b else print("-") if a == b else print("B")

Practical Examples

Ternary operators are particularly useful for simple assignments and return statements.

x = 15
y = 20
max_value = x if x > y else y
print("Maximum value:", max_value)

username = ""
display_name = username if username else "Guest"
print("Welcome,", display_name)

When to Use Shorthand If

Shorthand if statements and ternary operators should be used when:

• The condition and actions are simple
• It improves code readability
• You want to make a quick assignment based on a condition

Python Logical Operators

a = 200
b = 33
c = 500
if a > b and c > a:
  print("Both conditions are True")

a = 200
b = 33
c = 500
if a > b or a > c:
  print("At least one of the conditions is True")

a = 33
b = 200
if not a > b:
  print("a is NOT greater than b")

age = 25
is_student = False
has_discount_code = True

if (age < 18 or age > 65) and not is_student or has_discount_code:
  print("Discount applies!")

temperature = 25
is_raining = False
is_weekend = True

if (temperature > 20 and not is_raining) or is_weekend:
  print("Great day for outdoor activities!")

username = "Tobias"
password = "secret123"
is_verified = True

if username and password and is_verified:
  print("Login successful")
else:
  print("Login failed")

score = 85

if score >= 0 and score <= 100:
  print("Valid score")
else:
  print("Invalid score")

Python Nested If

Nested If Statements

You can have if statements inside if statements. This is called nested if statements.

Example

x = 41

if x > 10:
  print("Above ten,")
  if x > 20:
    print("and also above 20!")
  else:
    print("but not above 20.")

In this example, the inner if statement only runs if the outer condition (x > 10) is true.

How Nested If Works

Each level of nesting creates a deeper level of decision-making. The code evaluates from the outermost condition inward.

Example

Checking multiple conditions with nesting:

age = 25
has_license = True

if age >= 18:
  if has_license:
    print("You can drive")
  else:
    print("You need a license")
else:
  print("You are too young to drive")

Multiple Levels of Nesting

You can nest as many levels deep as needed, but keep in mind that too many levels can make code harder to read.

Example

Three levels of nesting:

score = 85
attendance = 90
submitted = True

if score >= 60:
  if attendance >= 80:
    if submitted:
      print("Pass with good standing")
    else:
      print("Pass but missing assignment")
  else:
    print("Pass but low attendance")
else:
  print("Fail")

Nested If vs Logical Operators

Sometimes nested if statements can be simplified using logical operators like and. The choice depends on your logic.

Example

This nested if:

temperature = 25
is_sunny = True

if temperature > 20:
  if is_sunny:
    print("Perfect beach weather!")

Example

Could also be written with and:

temperature = 25
is_sunny = True

if temperature > 20 and is_sunny:
  print("Perfect beach weather!")

Both approaches produce the same result. Use nested if statements when the inner logic is complex or depends on the outer condition. Use and when both conditions are simple and equally important.

More Examples

Example

Login validation with nested checks:

username = "Emil"
password = "python123"
is_active = True

if username:
  if password:
    if is_active:
      print("Login successful")
    else:
      print("Account is not active")
  else:
    print("Password required")
else:
  print("Username required")

Example

Grade calculation with nested logic:

score = 92
extra_credit = 5

if score >= 90:
  if extra_credit > 0:
    print("A+ grade")
  else:
    print("A grade")
elif score >= 80:
  print("B grade")
else:
  print("C grade or below")

Python Pass Statement

The pass Statement

if statements cannot be empty, but if you for some reason have an if statement with no content, put in the pass statement to avoid getting an error.

Example

a = 33
b = 200

if b > a:
  pass

The pass statement is a null operation - nothing happens when it executes. It serves as a placeholder.

Why Use pass?

The pass statement is useful in several situations:

• When you're creating code structure but haven't implemented the logic yet
• When a statement is required syntactically but no action is needed
• As a placeholder for future code during development
• In empty functions or classes that you plan to implement later

pass in Development

During development, you might want to sketch out your program structure before implementing the details. The pass statement allows you to do this without syntax errors.

Example

Placeholder for future implementation:

age = 16

if age < 18:
  pass # TODO: Add underage logic later
else:
  print("Access granted")

pass vs Comments

A comment is ignored by Python, but pass is an actual statement that gets executed (though it does nothing). You need pass where Python expects a statement, not just a comment.

Example

This will cause an error (empty code block):

score = 85

if score > 90:
  # This is excellent
# This will raise an IndentationError

Example

This works correctly with pass:

score = 85

if score > 90:
  pass # This is excellent
print("Score processed")

pass with Multiple Conditions

You can use pass in any branch of an if-elif-else statement.

Example

Using pass in different branches:

value = 50

if value < 0:
  print("Negative value")
elif value == 0:
  pass # Zero case - no action needed
else:
  print("Positive value")

pass in Other Contexts

While we focus on pass with if statements here, it's also commonly used with loops, functions, and classes.

Example

Using pass with functions:

def calculate_discount(price):
  pass # TODO: Implement discount logic

# Function exists but doesn't do anything yet