Python if elif else statements (With Examples)

5 minutes read
python control flows

By Lenin Mishra

The if statement in Python is similar to if statements in most procedural languages. It starts with an if test, followed by one or more optional elif (else if) tests and a final optional else block. The if-elif tests and the else part each have a block of nested statements, indented by 4 spaces or a tab.

When an if statement is executed, Python executes the block of code associated with the first test that evaluates to True, or the else block if all tests prove false.

Syntax of if, elif and else statements

if <test_1>: # if test
    <statement_1> # Associated nested block of if
elif <test_2>: # Optional elifs
    <statement_2> # Associated nested block of elif
else: # Optional else
    <statement_3>

Example 1

Let’s write a Python program to check if a number is odd or even.

Code

num = 12

if num%2 == 0:
    print("It is even")
else:
    print("It is odd")

Output

It is even

There is only 1 test being performed here - Checking of the remainder of a number divided by 2 is 0. If the test returns True, the number is declared even. You don’t have to write a second test to check if the number is odd. A number can either be even or odd. If the test returns False, the code in the else block gets executed.

Example 2

Let’s try out another example. Let’s write a Python program to check if a number is positive, negative or 0.

For this example, 2 tests need to be performed.

  1. Test 1 - Check if the number is positive
  2. Test 2 - Check if the number is negative
  3. If the number is neither positive nor negative, it is 0

Code

num = 10

if num > 0:
    print("It is positive")
elif num < 0:
    print("It is negative")
else:
    print("The number is 0")

Output

It is positive

The second test is used within an elif block. If your python program requires multiple tests, add as many elif blocks you want.

Example 3

Let’s write a Python program to check the status of a batsman’s score.

  1. Test 1 - Check if the batsman got out at 0. It’s a duck!
  2. Test 3 - Check if the batsman scored between 50 and 100. It’s a half century!
  3. Test 4 - Check if the batsman scored between 100 and 200. It’s a century!
  4. Test 5 - Check if the batsman score more than 200. It’s a double century!
  5. If none of the tests hold True, just print the score.

Code

score = 52

if score == 0:
    print("Duck")
elif score >= 50 and score < 100:
    print("Half century")
elif score >= 100 and score < 200:
    print("Century")
elif score >= 200:
    print("Double Century")
else:
    print(f"The score of the batsman is {score}")

Output

Half century

As you can see, we have multiple elif statements being used. Each statement covers a test scenario.

Example 4 - Experimenting with Booleans

In an if, elif, else decision making in Python, except the first test under the if block, every other test is optional. Once one of the tests is evaluated as True, the following tests are ignored.

Code - 1

if True:
    print("if block was executed.")
elif True:
    print("1st elif block was executed")
elif True:
    print("2nd elif block was executed")
else:
    print("Finally, else block was executed.")

Output

if block was executed.

Let’s add variations to the above code.

Code - 2

if False:
    print("if block was executed.")
elif True:
    print("1st elif block was executed")
elif True:
    print("2nd elif block was executed")
else:
    print("Finally, else block was executed.")

Output

1st elif block was executed

Code - 3

if False:
    print("if block was executed.")
elif False:
    print("1st elif block was executed")
elif True:
    print("2nd elif block was executed")
else:
    print("Finally, else block was executed.")

Output

2nd elif block was executed

Code - 4

if False:
    print("if block was executed.")
elif False:
    print("1st elif block was executed")
elif False:
    print("2nd elif block was executed")
else:
    print("Finally, else block was executed.")

Output

Finally, else block was executed.

Example 4 - Nested If statements

You can also nest if, elif, else statements inside of another if, elif, else block.

Let’s rewrite the Python program to check if a number is positive, negative or 0.

Code

num = -1

if num >= 0:
    if num == 0:
        print("The number is 0")
    else:
        print("It is positive")
else:
    print("It is a negative number")

Output

It is a negative number

Example 4 - Membership test of data types

Using the if, elif, else statements, you can check if a certain element exists in any data type.

Code

user_input = int(input("Enter a number ==> "))

my_list = [1, 2, 3]

if user_input in my_list:
    print(f"{user_input} was found")
else:
    print(f"Couldn't find {user_input}")

Output

Enter a number ==> 10
Couldn't find 10

You can use the in keyword to check for membership in any other data type.

Code

# Membership test for string

if "lenin" in "Pylenin":
    print("It exists")
else:
    print("Doesn't exist")

# Membership tests in tuples

my_tuple = (1, 2, 3, 4)

if 2 in my_tuple:
    print("It exists")
else:
    print("Doesn't exist")

# Membership tests in dictionary

my_dict = {"name":"Pylenin",
           "YOB": 1992}

if 'YOB' in my_dict.keys():
    print("It exists")
else:
    print("Doesn't exist")

Output

It exists
It exists
It exists

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