What is the naming convention in Python for variables and functions?

Python Naming Conventions: Variables and Functions

Explore the standard naming conventions in Python for variables and functions, including snake_case, PascalCase, and camelCase, and understand when to use each for cleaner, more readable code.

Python's PEP 8 style guide provides a comprehensive set of recommendations for writing readable and maintainable code. Adhering to these conventions, especially for naming variables and functions, is crucial for collaborating with other developers and ensuring your code is easily understood. This article will delve into the primary naming conventions used in Python, explaining their purpose and providing examples.

Snake Case: The Pythonic Standard

Snake case (snake_case) is the most common naming convention in Python, particularly for variables, functions, and module names. It involves using lowercase letters, with words separated by underscores. This convention is highly favored for its readability, especially in longer names.

# Variables
user_name = "Alice"
total_items_in_cart = 15

# Functions
def calculate_total_price(item_prices):
    return sum(item_prices)

def get_user_profile(user_id):
    # Imagine fetching user data
    return {"id": user_id, "name": "John Doe"}

Examples of variables and functions named using snake_case.

Pascal Case: Classes and Exceptions

Pascal case (PascalCase), also known as CapWords, is primarily used in Python for naming classes and exceptions. In this convention, the first letter of each word is capitalized, with no separators between words. This distinction helps differentiate classes from other identifiers in your code.

# Classes
class UserProfile:
    def __init__(self, name, email):
        self.name = name
        self.email = email

class DataProcessor:
    def process(self, data):
        return data.upper()

# Exceptions
class InvalidInputError(Exception):
    pass

class ConnectionTimeoutError(Exception):
    pass

Examples of classes and custom exceptions named using PascalCase.

Visual guide to Python naming conventions.

Camel Case: When to Avoid It

Camel case (camelCase), where the first letter of the first word is lowercase and subsequent words start with an uppercase letter, is common in languages like Java and JavaScript. However, in Python, camelCase is generally discouraged for variable and function names. While you might encounter it in some third-party libraries or frameworks that follow different conventions, it's best to stick to snake_case for your own Python code to maintain consistency with PEP 8.

# This is generally discouraged in Python for new code
# You might see it in some third-party libraries

def calculateTotalPrice(itemPrices):
    return sum(itemPrices)

userName = "Bob"

An example of camelCase (generally discouraged in Python).

Special Naming Conventions

Beyond the primary conventions, Python has a few special naming patterns that convey specific meanings or intentions:

• Single Leading Underscore (_variable): Indicates a 'private' or internal use variable/function. It's a convention, not an enforcement.
• Single Trailing Underscore (variable_): Used to avoid conflicts with Python's built-in keywords (e.g., class_, from_).
• Double Leading Underscore (__variable): Triggers name mangling, primarily used in classes to prevent name clashes in subclasses.
• Double Leading and Trailing Underscores (__variable__): Reserved for 'magic' methods or attributes (e.g., __init__, __str__). Avoid creating your own names using this pattern.

class MyClass:
    def __init__(self):
        self._internal_data = 10  # 'Private' convention
        self.name_ = "MyName"    # Avoids conflict with 'name' keyword
        self.__mangled_data = 20 # Name mangling

    def __str__(self):           # Magic method
        return "MyClass instance"

Examples of special naming conventions in Python.