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Aswin Barath
Aswin Barath

Posted on • Originally published at dev.to

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.

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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: Alt Text 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
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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:

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

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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:

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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:

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Output:

Largest number: 94
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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:

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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
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Code along and have fun.

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