Arguments and parameters in functions

In general, the term parameters and arguments are being used interchangeably.

Although, with respect to a function:

• parameters are the variables listed inside the parentheses in the function definition.
• arguments are the values that are sent to the function when it is called.

It turns out that it's possible to define functions with various types of arguments in python.
And there are three types of arguments/parameters, which can be combined.

1) Default Argument Values

• The most useful type of argument is to specify a default value for one or more arguments, inside the parenthesis of a function definition.
• This creates a function which is flexible to use.
• Because this function can be called with fewer arguments than it is defined to allow.
• Let's look at an example: Output:

You have 120 minutes!
Let's watch a action type web series
You have 150 minutes!
Let's watch a thriller type web series
You have 200 minutes!
Let's watch a horror type movie

This function is called in several ways:

• giving only the mandatory argument: popcorn_time(120)
• giving one of the optional arguments: popcorn_time(150, 'thriller')
• or even giving all arguments: popcorn_time(200, 'horror', 'movie')

Play with the code here

2) Keyword Arguments

• Functions can also be called using keyword arguments of the form kwarg=value.
• For instance, consider the above example of popcorn_time, function which accepts one required argument(time) and two optional arguments(genre, watch)
• This function can be called in any of the following ways:

• But take a note that, the following function calls would be invalid:

3) Special parameters

• By default, arguments may be passed to a Python function either by position or explicitly by keyword.
• For readability and performance, we can restrict the way arguments can be passed

• So, a developer needs to look at the function definition to determine if items are passed by position, by position or keyword, or by keyword.

• An advanced function definition may look like the one below:

• If you're interested, check out special parameters python docs for more information.

What if you don't know how many arguments you want to be passed into your function?
Python provides us with a solution:
Arbitrary Arguments - args
*Arbitrary Keyword Arguments - **kwargs

Arbitrary Arguments, *args

• To specify the argument as an arbitrary argument, you need to just add a *(asterisk) before the parameter name in the function definition.
• The function, in turn, will receive the arguments and save it as a tuple of arguments, and you can access the items accordingly:

Output:

Largest number: 94

Arbitrary Keyword Arguments, **kwargs

• Similarly, to specify the argument as an arbitrary keyword argument, you need to add two asterisks: ** before the parameter name in the function definition.
• The function, in turn, will receive the arguments and save it as a dictionary of arguments, and you can access the items accordingly:

Output:

Marvel Studios presents - Iron Man
Starring - Robert Downey Jr.
Marvel Studios presents - Captain America: The First Avenger
Starring - Chris Evans
Marvel Studios presents - Thor
Starring - Chris Hemsworth

Code along and have fun.