Conditional Statements

Conditional statements are used in programming to make decisions based on certain conditions. There are several types of conditional statements in Python.

The most basic type is the if-else statement. The if condition is used to evaluate a Boolean expression and execute a block of code only when the expression is true. If the expression is false, the else block of code is executed instead. The syntax for an if-else statement is:

if expression:
    statement(s)
else:
    statement(s)

Another type of conditional statement is the elif statement. This allows the programmer to evaluate more than one condition. If the first condition is false, the elif statement checks the next condition, and so on. The else block of code is executed if none of the conditions are true. The syntax for an if-elif-else statement is:

if expression1:
    statement(s)
elif expression2:
    statement(s)
elif expression3:
    statement(s)
else:
    statement(s)

Python also allows for nested if statements, where one if statement is placed inside another. This can be useful when the programmer needs to evaluate multiple conditions. The syntax for nested if statements is similar to the syntax for if-elif-else statements:

if expression1:
    statement(s)
    if expression2:
        statement(s)
    elif expression3:
        statement(s)
    elif expression4:
        statement(s)
    else:
        statement(s)
else:
    statement(s)

Finally, Python 3.10 introduced the match-case statement, which is similar to a switch statement in other programming languages. The match statement evaluates a variable and executes a block of code based on its value. The syntax for a match-case statement is:

match expression:
    case value1:
        statement(s)
    case value2:
        statement(s)
    case value3:
        statement(s)
    ...
    case valueN:
        statement(s)
    case _:
        statement(s)

The underscore (_) is used as a catch-all case for values that do not match any of the previous cases.

The ternary operator in Python is a concise way of writing an if-else statement in a single line. Its syntax takes the form of:

expression1 if condition else expression2

The condition is a boolean expression that evaluates to either True or False. If it is True, expression1 is returned; otherwise, expression2 is returned.

Using the ternary operator can make your code more concise and readable, especially for simple cases. For example, you can replace this if-else statement:

x = 5
if x > 0:
    y = "Positive"
else:
    y = "Non-positive"

with this one-liner using the ternary operator:

x = 5
y = "Positive" if x > 0 else "Non-positive"

The ternary operator can also be used as part of an expression, such as when initializing a variable:

y = 11
x = 5 if y > 0 else -5
# Output: 5

In this example, if y is greater than 0, x is assigned the value 5; otherwise, it is assigned the value -5.

It's important to note that overly complex expressions or long conditions can make code harder to read, so it's best to use the ternary operator for simple cases where the resulting code remains clear and easy to understand.