{"id":241,"date":"2020-10-05T04:47:51","date_gmt":"2020-10-05T04:47:51","guid":{"rendered":"https:\/\/www.pythontutorial.net\/?page_id=241"},"modified":"2025-03-26T12:43:07","modified_gmt":"2025-03-26T12:43:07","slug":"python-default-parameters","status":"publish","type":"page","link":"https:\/\/www.pythontutorial.net\/python-basics\/python-default-parameters\/","title":{"rendered":"Python Default Parameters"},"content":{"rendered":"\n

Summary<\/strong>: in this tutorial, you’ll learn about the Python default parameters to simplify function calls.<\/p>\n\n\n\n

Introduction to Python default parameters #<\/a><\/h2>\n\n\n\n

When you define a function<\/a>, you can specify a default value for each parameter.<\/p>\n\n\n\n

To specify default values for parameters, you use the following syntax:<\/p>\n\n\n

def<\/span> function_name<\/span>(param1, param2=value2, param3=value3, ...)<\/span>:<\/span><\/code><\/span>Code language:<\/span> Python<\/span> (<\/span>python<\/span>)<\/span><\/small><\/pre>\n\n\n
In this syntax, you specify default values (value2<\/code>, value3<\/code>, …) for each parameter using the assignment operator (=)<\/code>.<\/p>\n\n\n\n
When you call a  function and pass an argument to the parameter that has a default value, the function will use that argument instead of the default value.<\/p>\n\n\n\n
However, if you don’t pass the argument, the function will use the default value.<\/p>\n\n\n\n
To use default parameters, you need to place parameters with the default values after other parameters. Otherwise, you’ll get a syntax error. <\/p>\n\n\n\n
For example, you cannot do something like this:<\/p>\n\n\n
def function_name(param1=value1, param2, param3):<\/code><\/span><\/pre>\n\n\n
This causes a syntax error.<\/p>\n\n\n\n
Python default parameters example #<\/a><\/h2>\n\n\n\n
The following example defines the greet()<\/code> function that returns a greeting message:<\/p>\n\n\n
def<\/span> greet<\/span>(name, message='Hi'<\/span>)<\/span>:<\/span>\n    return<\/span> f\"{message}<\/span> {name}<\/span>\"<\/span><\/code><\/span>Code language:<\/span> Python<\/span> (<\/span>python<\/span>)<\/span><\/small><\/pre>\n\n\n
The greet()<\/code> function has two parameters: name<\/code> and message<\/code>. And the message<\/code> parameter has a default value of 'Hi'<\/code>.<\/p>\n\n\n\n
The following calls the greet()<\/code> function and passes the two arguments:<\/p>\n\n\n
def<\/span> greet<\/span>(name, message='Hi'<\/span>)<\/span>:<\/span>\n    return<\/span> f\"{message}<\/span> {name}<\/span>\"<\/span>\n\n\ngreeting = greet('John'<\/span>, 'Hello'<\/span>)\nprint(greeting)<\/code><\/span>Code language:<\/span> Python<\/span> (<\/span>python<\/span>)<\/span><\/small><\/pre>\n\n\n
Output:<\/p>\n\n\n
Hello John<\/code><\/span>Code language:<\/span> Python<\/span> (<\/span>python<\/span>)<\/span><\/small><\/pre>\n\n\n
Since we pass the second argument to the greet()<\/code> function, it uses the argument instead of the default value.<\/p>\n\n\n\n
The following example calls the greet()<\/code> function without passing the second argument:<\/p>\n\n\n
def<\/span> greet<\/span>(name, message='Hi'<\/span>)<\/span>:<\/span>\n    return<\/span> f\"{message}<\/span> {name}<\/span>\"<\/span>\n\n\ngreeting = greet('John'<\/span>)\nprint(greeting)<\/code><\/span>Code language:<\/span> Python<\/span> (<\/span>python<\/span>)<\/span><\/small><\/pre>\n\n\n
Output:<\/p>\n\n\n
Hi John<\/code><\/span>Code language:<\/span> Python<\/span> (<\/span>python<\/span>)<\/span><\/small><\/pre>\n\n\n
In this case, the greet()<\/code> function uses the default value of the message<\/code> parameter.<\/p>\n\n\n\n
Multiple default parameters #<\/a><\/h2>\n\n\n\n
The following redefines the greet()<\/code> function with the two parameters that have default values:<\/p>\n\n\n
def<\/span> greet<\/span>(name='there'<\/span>, message='Hi'<\/span>)<\/span>:<\/span>\n    return<\/span> f\"{message}<\/span> {name}<\/span>\"<\/span><\/code><\/span>Code language:<\/span> Python<\/span> (<\/span>python<\/span>)<\/span><\/small><\/pre>\n\n\n
In this example, you can call the greet()<\/code> function without passing any parameters:<\/p>\n\n\n
def<\/span> greet<\/span>(name='there'<\/span>, message='Hi'<\/span>)<\/span>:<\/span>\n    return<\/span> f\"{message}<\/span> {name}<\/span>\"<\/span>\n\n\ngreeting = greet()\nprint(greeting)<\/code><\/span>Code language:<\/span> Python<\/span> (<\/span>python<\/span>)<\/span><\/small><\/pre>\n\n\n
Output:<\/p>\n\n\n
Hi there<\/code><\/span>Code language:<\/span> Python<\/span> (<\/span>python<\/span>)<\/span><\/small><\/pre>\n\n\n
Suppose that you want the greet()<\/code> function to return a greeting like Hello there<\/code>. You may come up with the following function call:<\/p>\n\n\n
def<\/span> greet<\/span>(name='there'<\/span>, message='Hi'<\/span>)<\/span>:<\/span>\n    return<\/span> f\"{message}<\/span> {name}<\/span>\"<\/span>\n\n\ngreeting = greet('Hello'<\/span>)\nprint(greeting)<\/code><\/span>Code language:<\/span> Python<\/span> (<\/span>python<\/span>)<\/span><\/small><\/pre>\n\n\n
 Unfortuntely, it returns an unexpected value:<\/p>\n\n\n
Hi Hello<\/code><\/span>Code language:<\/span> Python<\/span> (<\/span>python<\/span>)<\/span><\/small><\/pre>\n\n\n
Because when you pass the 'Hello'<\/code> argument, the greet()<\/code> function treats it as the first argument, not the second one.<\/p>\n\n\n\n
def<\/span> greet<\/span>(name='there'<\/span>, message='Hi'<\/span>)<\/span>:<\/span>\n    return<\/span> f\"{message}<\/span> {name}<\/span>\"<\/span>\n\n\ngreeting = greet(message='Hello'<\/span>)\nprint(greeting)<\/code><\/span>Code language:<\/span> Python<\/span> (<\/span>python<\/span>)<\/span><\/small><\/pre>\n\n\n
 Output:<\/p>\n\n\n
Hello there<\/code><\/span>Code language:<\/span> Python<\/span> (<\/span>python<\/span>)<\/span><\/small><\/pre>\n\n\n
Summary #<\/a><\/h2>\n\n\n\n
Try it<\/a><\/p>\n\n\n\n
To resolve this, you need to call the greet()<\/code> function using keyword arguments<\/a> like this:<\/p>\n\n\n
Try it<\/a><\/p>\n\n\n\n
Try it<\/a><\/p>\n\n\n\n
Try it<\/a><\/p>\n\n\n\n
Try it<\/a><\/p>\n\n\n\n