Python - if , if..else, Nested if, if-elif statements

There are situations in real life when we need to do some specific task and based on some specific conditions, we decide what we should do next. Similarly, there comes a situation in programming where a specific task is to be performed if a specific condition is True. In such cases, conditional statements can be used. The following are the conditional statements provided by Python. 

1. if
2. if..else
3. Nested if
4. if-elif statements.

Let us go through all of them.

if Statement in Python

If the simple code of block is to be performed if the condition holds true then the if statement is used. Here the condition mentioned holds then the code of the block runs otherwise not.

Python if Statement Syntax

if condition:

# Statements to execute if condition is true

Flowchart of if Statement in Python

Below is the flowchart by which we can understand how to use if statement in Python:

Example: Basic Conditional Check with if Statement

In this example, an if statement checks if 10 is greater than 5. If true, it prints "10 greater than 5"; regardless, it then prints "Program ended" as the next statement, indicating the program flow.

# if statement example
if 10 > 5:
    print("10 greater than 5")

print("Program ended")

10 greater than 5
Program ended

Indentation(White space) is used to delimit the block of code. As shown in the above example it is mandatory to use indentation in Python3 coding.

if else Statement in Python

In conditional if Statement the additional block of code is merged as else statement which is performed when if condition is false. 

Python if-else Statement Syntax  

if (condition):

# Executes this block if condition is true

else:

# Executes this block if condition is false

Flow Chart of if-else Statement in Python

Below is the flowchart by which we can understand how to use if-else statement in Python:

Example 1: Handling Conditional Scenarios with if-else

In this example, the code assigns the value 3 to variable x and uses an if..else statement to check if x is equal to 4. If true, it prints "Yes"; otherwise, it prints "No," demonstrating a conditional branching structure.

# if..else statement example
x = 3
if x == 4:
    print("Yes")
else:
    print("No")

No

Example 2: Nested if..else Chain for Multiple Conditions

You can also chain if..else statement with more than one condition. In this example, the code uses a nested if..else chain to check the value of the variable letter. It prints a corresponding message based on whether letter is "B," "C," "A," or none of the specified values, illustrating a hierarchical conditional structure.

# if..else chain statement
letter = "A"

if letter == "B":
    print("letter is B")

else:

    if letter == "C":
        print("letter is C")

    else:

        if letter == "A":
            print("letter is A")

        else:
            print("letter isn't A, B and C")

letter is A

Nested if Statement

if statement can also be checked inside other if statement. This conditional statement is called a nested if statement. This means that inner if condition will be checked only if outer if condition is true and by this, we can see multiple conditions to be satisfied.

Python Nested If Statement Syntax

if (condition1):

# Executes when condition1 is true

if (condition2):

# Executes when condition2 is true

Flow chart of Nested If Statement In Python

Below is the flowchart by which we can understand how to use nested if statement in Python:

Example: Managing Nested Conditions for Refined Control

In this example, the code uses a nested if statement to check if the variable num is greater than 5. If true, it further checks if num is less than or equal to 15, printing "Bigger than 5" and "Between 5 and 15" accordingly, showcasing a hierarchical condition for refined control flow.

# Nested if statement example
a = 10

if a > 5:
    print("Bigger than 5")

    if a <= 15:
        print("Between 5 and 15")

Bigger than 5
Between 5 and 15

if-elif Statement in Python

The if-elif statement is shortcut of if..else chain. While using if-elif statement at the end else block is added which is performed if none of the above if-elif statement is true.

Python if-elif Statement Syntax

if (condition):

statement

elif (condition):

statement

else:

statement

Flow Chart of Python if-elif Statement

Below is the flowchart by which we can understand how to use elif in Python:

Sequential Evaluation with if-elif-else Structure

In this example, the code uses an if-elif-else statement to evaluate the value of the variable letter. It prints a corresponding message based on whether letter is "B," "C," "A," or none of the specified values, demonstrating a sequential evaluation of conditions for controlled branching.

# if-elif statement example
letter = "A"

if letter == "B":
    print("letter is B")

elif letter == "C":
    print("letter is C")

elif letter == "A":
    print("letter is A")

else:
    print("letter isn't A, B or C")

letter is A

Can We Use Elif in Nested If?

Yes, you can use elif within nested if statements in Python. This allows for more complex decision structures within a branch of another decision. For example:

x = 10
y = 5
if x > 5:
    if y > 5:
        print("x is greater than 5")
    elif y==5:
         print("x is greater than 5 and y is 5")
    else:
        print("x is greater than 5 and y is less than 5")

x is greater than 5 and y is 5

The structure of the above code provides conditional checks within another conditional check, enhancing the decision-making capabilities of your code.

Are You Allowed to Nest If Statements Inside Other If Statements in Python?

Yes, you are allowed to nest if statements inside other if statements in Python. This is a common practice used to make more complex conditional logic possible. Nested if statements can be as deep as you need, although deep nesting can make your code harder to read and maintain.

shivalibhadaniya

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