Understanding Python Keyword-Only Arguments

In Python, keyword-only arguments are parameters that must be specified by name when calling a function. This feature improves code readability and helps prevent common errors associated with passing arguments.

Key Concepts

• Keyword-Only Arguments: These arguments can only be passed by explicitly naming them in the function call.
• Syntax: A keyword-only argument is defined by placing an asterisk (*) before the argument name in the function definition.

Why Use Keyword-Only Arguments?

• Clarity: They make function calls clearer, especially when numerous parameters are involved.
• Prevent Errors: They help avoid mistakes by ensuring that the argument is explicitly named.

Example

Here’s a simple example to illustrate keyword-only arguments:

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

# Calling the function
print(greet('Alice'))                # Output: Hello, Alice!
print(greet('Bob', greeting='Hi'))   # Output: Hi, Bob!

Explanation of the Example:

• In the greet function:
  • name is a positional argument that can be passed normally.
  • greeting is a keyword-only argument, meaning it must be specified by name when calling the function.
• The first call to greet('Alice') uses the default value for greeting.
• The second call specifies greeting='Hi', demonstrating how to use a keyword-only argument.

Conclusion

Keyword-only arguments are a powerful feature in Python that enhances function definition and usage. By requiring explicit names for certain parameters, they help make code more readable and less error-prone.