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In Python, the elif statement consists of three parts:

• An if statement with its associated condition.
• An elif statement with its associated condition.
• Finally, an optional else statement, which has no condition associated with it.

Note: In many languages, an elif statement is known as the else-if statement.

Working of elif

• First the condition in the parenthesis of the if statement is evaluated for a boolean value - true or false.


• If the condition with the if statement is true, then the statement or a block of statements connected to it is executed.


• If the condition with the if statement is false, only then the condition associated with elif is evaluated.


• In that case, if the condition with the elif statement is true, then the statement or a block of statements connected to it is executed.


• But, if the condition of the elif is evaluated to be false, then the statement or a block of statements connected to the underneath optional else(if declared) is executed.

Important points about conditional statements in Python

• As you can see in the diagram above, In Python, a colon: is required after declaring the condition of a conditional statement, be it an if, elif, etc, which helps us in declaring the start of an upcoming indented block and it also improves readability.


• In Python, the condition of an if, elif statement can even be declared without a pair of parentheses () around it(contrary to many programming languages like C, C++ which require us to wrap a condition within a pair of parentheses).


• Unlike many programming languages like C, C++, Java which require a pair of braces { } to hold multiple statements associated with a conditional statement like if, else, etc, the Python language does not require you to use a pair of braces { } to contain one or more statements with any conditional statement.


• Using a pair of braces { } to hold one or more statements with any conditional statement like if or else statement gives an error.


• Q: Then how do we associate one or multiple statements with a conditional statement like if, elif or else?
  A: In Python, indentation is meaningful and using it we can associate one or more statements with any conditional statement.

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else if statement example

# Python - else-if statement example

if(99>100):
	print("99 is greater than 100")
elif(99<90):
	print("99 is less than 90")
print"(Statement not connected to elif statement")

Output

Statement not connected to elif statement

Program Analysis

• The if statement condition i.e. 99>100 is false, hence its associated print statement is not executed.
• Because the condition of the if statement is evaluated to be false, therefore the condition of the elif statement i.e. 99<99 is evaluated, which turned out to be false and hence its associated statement is not executed.
• The print statement outside the if-elif block is executed without an issue because it is not associated with the elif statement, due to the absence of its indentation with it.

elif statement with an optional else statement

# Python - elif statement with an optional else statement example

if(99>100):
	print("99 is greater than 100")
elif(99<90):
	print("99 is less than 90")
else:
	print("99 is greater than 90 and less than 100")
print"(Statement not connected to elif statement")

Output

99 is greater than 90 and less than 100
Statement not connected to elif statement

Program Analysis

• The if statement condition i.e. 99>100 is false, hence its associated print statement is not executed.
• Because the condition of if statement is evaluated to be false, therefore the condition of elif statement i.e. 99<99 is evaluated, which turned out to be false and hence its associated statement is not executed.
• Because the condition of elif statement is evaluated to be false, hence the print statement associated with the optional else statement is executed.
• The print statement outside the if-elif block is executed without an issue because it is not associated with the optional else statement, due to the absence of its indentation with it.






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