This is the fourth blog on Python for fintch professionals.
What Are Functions in Python?
In Python, functions are defined blocks of reusable code that perform specific tasks. They are invoked using their names followed by parentheses. For example:
print()
Functions can accept arguments placed within the parentheses, which may be mandatory or optional. If a required argument is not provided, the code will raise an error.
Types of Arguments
1. Positional Arguments
The meaning of these arguments is determined by their position in the function call.
2. Keyword Arguments
These can have default values assigned, such as sep="\n". Keyword arguments must be placed after positional arguments in the function call.
You can override default values by providing your own values for keyword arguments. For example:
print('My', 'name', 'is', 'Monty', 'Python.', sep='_')
This would output: My_name_is_Monty_Python.
However, if you forget the comma between arguments:
print('My', 'name', 'is', 'Monty', 'Python' sep='_')
This will raise a syntax error.
Each function must be defined on its own line. Placing two function definitions on a single line will result in an error. Functions can span multiple lines if necessary, which is useful for longer definitions.
What Can Functions Do?
Functions can:
Cause an Effect: For example, the `print` function outputs text to the terminal.
Evaluate a Value: Functions can perform computations and return results.
Sources of Python Functions
Functions can be sourced from various places, including:
Built-in Functions: Python comes with a rich set of built-in functions, detailed in the Python Standard Library documentation.
Modules: You can import functions from standard or third-party modules, often installed via package managers like PIP.
Custom Functions: You can also define your own functions to meet specific needs.
How to Write a Python Function
To define a function in Python, start with the "def" keyword, followed by the function name and parentheses containing any arguments. The definition ends with a colon. Here’s the basic structure:
def function_name(argument):
# Function body goes here
Ensure that your function name is not a reserved keyword in Python, such as "True".
Methods vs. Functions
A method is similar to a function but is associated with an object and is called on that object using dot notation. Each data type has its own set of methods. For example:
'i am a string'.capitalize() # This capitalizes the string.
Or, using a variable:
text = 'i am a string
print(text.upper()) # This converts the string to uppercase.
Conclusion
Functions are a fundamental concept in Python, enabling code reuse and modular programming. Understanding how to define and use them effectively is essential for writing efficient and organized Python code.