Function Definition

What is a Function?#

In Python, a function is a block of organized, reusable code that is used to perform a specific action. It provides better modularity for your application and promotes code reusability.

How to Define a Function?#

Functions in Python are defined using the def keyword, followed by a function name and parentheses (()). Any input parameters should be placed within these parentheses, and the function’s body is indented under the function definition. The syntax is as follows:

1def function_name(parameter1, parameter2):
2    # statements to be executed within the function
3    pass

Here, function_name is the name of the function, parameter1 and parameter2 are parameters which are inputs to your function, and pass is a Python statement that does nothing. It can be used when a statement is required syntactically but the function does not need to execute any code.

For instance, let’s create a simple function that greets anyone based on the name passed as a parameter:

1def greet(name):
2    print(f"Hello, {name}. Nice to meet you!")
3
4# Now, we can call our function:
5greet("Alice")

Running this code prints "Hello, Alice. Nice to meet you!".

Docstrings#

Docstrings, also known as documentation strings, are descriptive text strings enclosed with triple quotes (""" ... """). They provide a way of commenting Python functions, methods, modules and classes. A docstring is associated with the object as their __doc__ attribute. For functions, the docstring is a line that comes immediately after the function definition, and is used for explaining what the function does.

1def greet(name):
2    """
3    This function greets a
4    person passed in as a parameter
5    """
6    print(f"Hello, {name}. Nice to meet you!")
7    
8# We can access the docstring using the __doc__ attribute
9print(greet.__doc__)

This would print:

This function greets a
person passed in as a parameter

Docstrings are a good programming practice, as they make your code more readable and accessible for other developers or even your future self.