Conditional Statement if-else in Python

Conditional Statement

In real life, there are times when we must make decisions and then decide what to do next base on those decisions. Similar circumstances exist in programming, where we must make decisions and then execute the following block of code based on those decisions. In programming languages, decision-making statements determine the course of programme execution.

There are different types of Decision making Statement.

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

If Statement

The, if condition is the most basic decision-making condition. It is used to determine if a statement or a block of statements will be executed or not, i.e., if a condition is true, a block of statements will be executed; otherwise, it will not.

Syntax:

if condition:    # Statements to execute if    # condition is true

 

After examination, the condition will be either true or false. If the value is true, the if statement will execute the block of statements below it; otherwise, it will not. We can also use a condition using the bracket '(' ')'.

Python uses indentation to distinguish blocks, as we all know. As seen in the example below, the block under an if statement will be identified:

 Syntax:

if condition:    statement1 statement2

# Here if the condition is true, if block # will consider only statement1 to be inside # Its block.

 

Flowchart of Python if statement

Example:

#Write a Python Program to illustrate If statement   i = 10   if (i > 15):     print("10 is less than 15") print("If Statement Fails")

Output If Statement Fails

Because the if statement's condition is false. As a result, the block below the if statement is skipped.

If-else Statement

If a condition is true, the if statement will execute a block of statements; if the condition is false, the if statement will not. But what if the condition is false and we want to do something else? This is when the otherwise statement comes in. When the condition is false, we can combine the else statement with the if statement to execute a block of code.

Syntax:

if (condition):     # Executes this block if     # condition is true else:     # Executes this block if     # condition is false

Flowchart of Python if statement

Example:

# Write a Python Program to illustrate If else statement   i = 22 if (i < 15):             print("i is smaller than 15")             print("Else Statement Fails") else:             print("i is greater than 15")             print("If Statement Fails")

Output:  i is greater than 15 If Statement Fails

 

After calling the statement that is not in block, the block of code following the else statement is performed because the condition in the if statement is false (without spaces).

Nested If-else

An if statement that is the target of another if statement is known as a nested if. An if statement inside another if statement is referred to as nested if statements. Yes, we may stack if statements within if statements in Python. We can put an if statement inside another if statement, for example.

Syntax:

if (condition1):    # Executes when condition1 is true    if (condition2):       # Executes when condition2 is true    # if Block is end here # if Block is end here

Flow Chart in Nested if-else

Example:

# Write a Python Program to illustrate nested If statement   i = 10 if (i == 10):               # First if statement               if (i < 15):                         print("i is smaller than 15")                                     # Nested - if statement             # Will only be executed if statement above             # it is true               if (i < 12):                         print("i is smaller than 12 too")             else:                         print("i is greater than 15") else:                print(“i is less than 10”)

Output i is smaller than 15 i is smaller than 12 too

 

if-elif-else ladder

A user can choose from a variety of alternatives here. From the top down, the if statements are performed. The statement linked with that if is performed as soon as one of the criteria controlling the if is true, and the rest of the ladder is bypassed. The last else line will be performed if none of the criteria are true.

Syntax:

if (condition):     statement elif (condition):     statement . . else:     statement

 

Flow Chart of If-elif-else Ladder Statement

Example:

# Write a Python Program to illustrate if-elif-else ladder   i = 35 if (i == 10):             print("i is 10") elif (i == 25):             print("i is 25") elif (i == 35):             print("i is 35") else:             print("i is not present")

Output: i is 35