tags: #python/documentation/python_functions

Understanding Parameters and Arguments

Parameters

Parameters are variables defined in the function. The parameters act a placeholders that get replaced with the input values that the function expects when it is called.

Arguments

An argument is the actual value that is passed through the function when it is called. This value is assigned to the corresponding parameter defined inside the function.

When invoking a function, a value should be provided to each associated parameters.

How can we arguments be specified?

There are 2 ways arguments can be passed. However, by default, parameters have a positional behaviour (exception: named arguments, which can be given in any order).

Positional Passing

Positional arguments are values that are passed into a function based on the order in which the parameters were listed during the function definition.

In this case, the order is especially important as values passed into these functions are assigned to corresponding parameters based on their position.

def greet(name, age):
    print(f"Hello, {name}! You are {age} years old.")

greet("Alice", 25)

Keyword-Based Passing

Keyword arguments can be likened to dictionaries in that they map a value to a keyword (parameter) defined in the function:

kwarg = {parameter: argument, ...}

myFunction(**kwargs)

This is a way to pass any number of named arguments to a function, which Python collects into a dictionary inside the function.

def greet(name, age, city):
    print(f"Hello {name}, age {age}, from {city}")

data = {"name": "Bob", "age": 25, "city": "Vancouver"}
greet(**data)    # same as greet(name="Bob", age=25, city="Vancouver")

This is most useful when there are many optional parameters and you want to provide a value for only a select few.