6.3. Functions in Python: Function Calls
Functions are one of the most fundamental and powerful elements in the Python programming language. They allow programmers to bundle a set of instructions into a single block of code that can be called and reused in different parts of the program. This not only makes the code cleaner and easier to read, but also makes the code easier to maintain and debug.
Defining Functions
In Python, a function is defined using the 'def' keyword, followed by the function name and a pair of parentheses (). Within these parentheses, you can include any parameters that the function must accept. Parameters are variables that will be used within the function. After the parentheses, you include a colon (:) to indicate the start of the function's code block. The function code block is indented relative to the function definition line. See an example:
def my_function(parameter1, parameter2):
# function code block
result = parameter1 + parameter2
return result
Here, 'my_function' is the name of the function, 'parameter1' and 'parameter2' are the parameters, and the function code block calculates the sum of the parameters and returns the result.
Calling Functions
Once a function is defined, you can call it anywhere in your program. To call a function, you use the name of the function followed by a pair of parentheses (). Inside those parentheses, you include the arguments you want to pass to the function. Arguments are the actual values you want the function to use. See an example:
result = my_function(5, 3) print(result) # prints 8
Here, we are calling the function 'my_function' with arguments 5 and 3. The function calculates the sum of these numbers and returns the result, which is then stored in the variable 'result' and printed.
Functions without Parameters
Some functions may not need any parameters to work. In this case, you still include the pair of parentheses () when defining and calling the function, but you don't put anything inside them. Here is an example:
def say_hello():
print("Hello world!")
say_hello() # prints "Hello world!"
In this example, the 'say_hello' function does not accept any parameters. When we call the function, it simply prints the string "Hello world!".
Functions with Return Values
Functions can return a value that can be used elsewhere in the program. This is done using the 'return' keyword. When the execution of a function reaches a 'return' statement, the function terminates immediately and the value after the 'return' keyword is the result of the function. Here is an example:
def square(n):
return n ** 2
print(square(4)) # prints 16
In this example, the 'square' function accepts a 'n' parameter and returns the square of that number. When we call the function with the argument 4, it returns 16, which is then printed.
In short, functions in Python are a powerful tool that lets you wrap a set of statements into a single block of code that can be called and reused in different parts of the program. They make code cleaner, easier to read, and easier to maintain.
