What are the best practices for using default arguments in Python?

What are the best practices for using default arguments in Python?

Using default arguments can simplify function calls, but there are some best practices to follow. First, ensure that default values are immutable types like strings or tuples to avoid unexpected behavior. Also, place default arguments at the end of the parameter list to maintain clarity.

Can you give an example of a function with default arguments?

Sure! Here's a simple example:

def greet(name, greeting='Hello'):
    return f'{greeting}, {name}!'

In this function, greeting has a default value of 'Hello'. If you call greet('Alice'), it returns 'Hello, Alice!'. If you call greet('Alice', 'Hi'), it returns 'Hi, Alice!'.

What should I avoid when using default arguments?

Avoid using mutable types like lists or dictionaries as default arguments. For example:

def append_to_list(value, my_list=[]):
    my_list.append(value)
    return my_list

This can lead to unexpected behavior because the same list is used across all calls.

How can I handle mutable default arguments properly?

You can handle mutable default arguments by setting the default to None and then initializing the mutable object inside the function:

def append_to_list(value, my_list=None):
    if my_list is None:
        my_list = []
    my_list.append(value)
    return my_list

This way, a new list is created for each function call.