Decision-making is a crucial aspect of programming, allowing a program to make choices based on certain conditions or inputs. In Python, decision-making is achieved through the use of control structures such as if-else statements and loops.

If-Else Statements

The most basic form of decision-making in Python is the if-else statement.

The syntax for an if-else statement is as follows:

if condition:
    # code to be executed if condition is true
else:
    # code to be executed if condition is false

The condition in an if-else statement is a Boolean expression that evaluates to either True or False.

Here is an example of if-else statement:

x = 5
if x > 0:
    print("x is positive")
else:
    print("x is negative or zero")
# Output : x is positive

If-Elif-Else Statements

• In some cases, you may want to check multiple conditions and execute different codes for each condition.
• This can be done using the if-elif-else statement, which allows for multiple conditions to be checked.

if condition1:
    # code to be executed if condition1 is true
elif condition2:
    # code to be executed if condition1 is false and condition2 is true
else:
    # code to be executed if condition1 and condition2 are both false

An example of if-elif-else statement:

x = 5
if x > 0:
    print("x is positive")
elif x == 0:
    print("x is zero")
else:
    print("x is negative")

Nested If-Else Statements

• It is also possible to have if-else statements inside other if-else statements. These are called nested if-else statements.
• The inner if-else statements will only be executed if the outer if-else statement's condition is true.

The syntax for a nested if-else statement is as follows:

if condition1:
    if condition2:
        # code to be executed if condition1 and condition2 are true
    else:
        # code to be executed if condition1 is true and condition2 is false
else:
    # code to be executed if condition1 is false

An example of nested if-else statement:

x = 5
y = 10
if x > 0:
    if y > 0:
        print("x and y are both positive")
    else:
        print("x is positive and y is non-positive")
else:
    print("x is non-positive")

Conditional Expressions

Python has a shorthand notation for simple if-else statements, called a conditional expression.

The syntax for a conditional expression is as follows:

value_if_true if condition else value_if_false

An example of if-else shorthand:

x = 5
result = "positive" if x > 0 else "non-positive"
print(result)

Conclusion

• Decision-making in Python is achieved through the use of control structures such as if-else statements and loops.
• The if-else statement is used to check a single condition and execute different codes based on whether the condition is true or false.
• The if-elif-else statement allows for multiple conditions to be checked.
• Nested if-else statements can be used to check multiple conditions in a more complex manner.
• Conditional expressions provide a shorthand notation for simple if-else statements.