Conditional Statements in Python: A Guide

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Python supports the usual logical conditions from mathematics:

• Equals : a == b
• Not Equals : a != b
• Less than: a < b
• Less than or equal to a <= b
• Greater than: a > b
• Greater than or equals to a ≥ b

These conditions can be used in several ways most commonly in “if statements” and loops.

Decision-making statements in programming language decide the direction of the flow of program execution. The decision-making statements available in Python are:-

• If statement
• if…else statement
• if…elif…else statement
• nested if statements

Introduction to the if Statement

• An “if statement” is written by using the if keyword.
• The if statement is the most simple decision-making statement.
• It is used to decide whether a certain statement or block of statements will be executed or not.
• That is, if a certain condition is true then a block of statement is executed otherwise not.

Syntax:

We can use if condition with bracket ‘(‘ ‘)’ also.

Flowchart:

As the condition present in the if statement is false. So, the block below the if statement is not executed.

Program:

if condition is True then only print statement will execute

Output:

It is raining will execute anyways because it is outside the body of the loop

If-else Statements

• The if statement alone tells us that if a condition is true it will execute a block of statements and if the condition is false it won’t
• But what if we want to do something else if the condition is false.
• Here comes the else statement.
• We can use the else statement with the if statement to execute a block of code when the condition is false.
• If the condition is true, the first statement [if] is executed, and the second [else] is skipped. If the condition is false, the first statement [if] is skipped and the second [else] is executed. Either way, execution then resumes after the second condition. Both conditions are defined by indentation.

Syntax :-

Flowchart:-

Program:-

• Here, else statement will execute because the if condition is false

Output:-

if-elif-else statements

• The if-elif-else statements are like a ladder of if and else statements. There can be multiple elif statements
• The elif statement also has its condition so, if the elif condition is true, it will execute the elif statement
• Here the else statement will only execute if both of the if and elif statements are false
• Here, a user can decide among multiple options. The if statements are executed from the top down.
• As soon as one of the conditions controlling the if is true, the statement associated with that if is executed, and the rest of the ladder is bypassed. If none of the conditions is true, then the final else statement will be executed.

Syntax:

Flowchart:

Program:

Output:

Nested-if Statements

• Python allows us to nest if statements within if statements
• eg, We can place an if statement inside another if statement.
• A nested if is an if statement that is the target of another if statement.
• We can have a number of if statement corresponds to its else statements.

Syntax:

Flowchart:

Program:

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