How do we define a function in Python? Provide an example.
A function in Python is a block of reusable code that performs a specific task. It allows you to organize your code into modular and reusable components, making your program more efficient, readable, and maintainable. Defining a function involves specifying its name, parameters, and the code block that is executed when the function is called.
To define a function in Python, you use the `def` keyword followed by the function name and a pair of parentheses. Inside the parentheses, you can optionally specify one or more parameters that the function accepts. These parameters act as placeholders for the values that will be passed to the function when it is called.
The code block of the function is defined by indenting it below the function definition line. This code block can contain any valid Python statements, including variable declarations, conditional statements, loops, and other function calls. It is executed when the function is called and can optionally return a value using the `return` statement.
Here's an example of a simple function that calculates the sum of two numbers:
python
def add_numbers(a, b):
sum = a + b
return sum
In this example, the function is named `add_numbers` and it accepts two parameters `a` and `b`. Inside the function, the sum of `a` and `b` is calculated and stored in the variable `sum`. Finally, the `return` statement is used to return the value of `sum` back to the caller.
To call this function and use its result, you simply write the function name followed by the arguments enclosed in parentheses:
python result = add_numbers(5, 3) print(result) # Output: 8
In this case, the function `add_numbers` is called with the arguments `5` and `3`, and the returned value `8` is assigned to the variable `result`. The `print` statement then outputs the value of `result`.
Functions can also have default parameter values, allowing you to call the function with fewer arguments. For example:
python
def greet(name, greeting="Hello"):
message = f"{greeting}, {name}!"
return message
print(greet("Alice")) # Output: Hello, Alice!
print(greet("Bob", "Hi")) # Output: Hi, Bob!
In this example, the `greet` function has a default parameter value for `greeting`, which is set to `"Hello"`. If only the `name` argument is provided when calling the function, the default value is used. However, you can also explicitly specify a different value for `greeting`, as shown in the second `print` statement.
A function in Python is defined using the `def` keyword followed by the function name, optional parameters, and a code block. The function can be called with arguments, and it can optionally return a value using the `return` statement. Functions help organize code, promote reusability, and enhance the overall structure and readability of Python programs.
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