Parameter vs. argument

In programming, the terms "parameter" and "argument" are often used interchangeably, but they have distinct meanings. Understanding the difference between them is important for clear communication, especially when discussing functions, methods, and their calls.

Parameters

Parameters are variables that are used in the function signature to define what kind of values the function expects to receive when it is called. You can think of parameters as placeholders in a function definition. They define the type and number of values that functions need to perform their tasks.

Example in Python:

def add(a, b):  # 'a' and 'b' are parameters
    return a + b

In this example, a and b are parameters of the function add. They indicate that the function requires two inputs to operate.

Arguments

Arguments, on the other hand, are the actual values or data that you pass to the function when you call it. These are the specific instances of data that replace the parameters when the function is executed.

Example in Python:

result = add(5, 3)  # '5' and '3' are arguments
print(result)

Here, 5 and 3 are arguments provided to the function add. These arguments are the actual values that the function uses to perform its operation, in this case, adding the two numbers.

Summary

• Parameters are the variables listed in the function definition and act as placeholders for the values that will be provided when the function is called.
• Arguments are the actual values or data passed to the function when it is called. They replace the parameters with real values during function execution.

Additional Insights

Formal vs. Actual Parameters

Another way to describe these concepts is to use the terms "formal parameters" and "actual parameters":

• Formal Parameters: Another term for parameters, emphasizing that they are part of the formal definition of the function.
• Actual Parameters: Another term for arguments, emphasizing that they are the actual data provided to the function.

Keyword and Positional Arguments

In languages like Python, arguments can be further classified based on how they are specified in a function call:

• Positional Arguments: Arguments that need to be included in the proper position or order. The first argument provided fills the first parameter, and so on.
• Keyword Arguments: Arguments that are explicitly assigned to a parameter by name, allowing them to be passed in a different order from the one specified in the function definition.

Default Parameters

Parameters can have default values, which make them optional during function calls. If an argument for a parameter with a default value is not provided, the default value is used.

Example:

def log(message, level='INFO'):
    print(f"[{level}] - {message}")

log('User logged in.')  # Uses the default level of 'INFO'
log('User logged out.', level='DEBUG')  # Uses 'DEBUG' as the level

Understanding the distinction between parameters and arguments is crucial for effective coding and communication, especially when working with functions in any programming language.