{"id":1006,"date":"2020-11-10T01:21:32","date_gmt":"2020-11-10T01:21:32","guid":{"rendered":"https:\/\/www.pythontutorial.net\/?page_id=1006"},"modified":"2025-03-27T13:54:01","modified_gmt":"2025-03-27T13:54:01","slug":"python-decorator-arguments","status":"publish","type":"page","link":"https:\/\/www.pythontutorial.net\/advanced-python\/python-decorator-arguments\/","title":{"rendered":"Python Decorator with Arguments"},"content":{"rendered":"\n

Summary<\/strong>: in this tutorial, you’ll learn how to define Python decorators with arguments using a decorator factory.<\/p>\n\n\n\n

Introduction to Python decorator with arguments #<\/a><\/h2>\n\n\n\n

Suppose that you have a function<\/a> called say<\/code> that prints out a message:<\/p>\n\n\n

def<\/span> say<\/span>(message)<\/span>:<\/span>\n    ''' print the message \n    Arguments\n        message: the message to show\n    '''<\/span>\n    print(message)<\/code><\/span>Code language:<\/span> Python<\/span> (<\/span>python<\/span>)<\/span><\/small><\/pre>\n\n\n
and you want to execute the say()<\/code> function 5 times repeatedly each time you call it. For example:<\/p>\n\n\n
say('Hi'<\/span>)<\/code><\/span>Code language:<\/span> Python<\/span> (<\/span>python<\/span>)<\/span><\/small><\/pre>\n\n\n
It should show the following the Hi<\/code> message five times as follows:<\/p>\n\n\n
Hi\nHi\nHi\nHi\nHi<\/code><\/span><\/pre>\n\n\n
To do that, you can use a regular decorator<\/a>:<\/p>\n\n\n
@repeat<\/span>\ndef<\/span> say<\/span>(message)<\/span>:<\/span>\n    ''' print the message \n    Arguments\n        message: the message to show\n    '''<\/span>\n    print(message)\n<\/code><\/span>Code language:<\/span> Python<\/span> (<\/span>python<\/span>)<\/span><\/small><\/pre>\n\n\n
And you can define the repeat<\/code> decorator as follows:<\/p>\n\n\n
def<\/span> repeat<\/span>(fn)<\/span>:<\/span>\n    @wraps(fn)<\/span>\n    def<\/span> wrapper<\/span>(*args, **kwargs)<\/span>:<\/span>\n        for<\/span> _ in<\/span> range(5<\/span>):\n            result = fn(*args, **kwargs)\n        return<\/span> result\n\n    return<\/span> wrapper    <\/code><\/span>Code language:<\/span> Python<\/span> (<\/span>python<\/span>)<\/span><\/small><\/pre>\n\n\n
The following shows the complete code:<\/p>\n\n\n
from<\/span> functools import<\/span> wraps\n\ndef<\/span> repeat<\/span>(fn)<\/span>:<\/span>\n    @wraps(fn)<\/span>\n    def<\/span> wrapper<\/span>(*args, **kwargs)<\/span>:<\/span>\n        for<\/span> _ in<\/span> range(5<\/span>):\n            result = fn(*args, **kwargs)\n        return<\/span> result\n\n    return<\/span> wrapper\n\n\n@repeat<\/span>\ndef<\/span> say<\/span>(message)<\/span>:<\/span>\n    ''' print the message \n    Arguments\n        message: the message to show\n    '''<\/span>\n    print(message)\n\n\nsay('Hello'<\/span>)<\/code><\/span>Code language:<\/span> Python<\/span> (<\/span>python<\/span>)<\/span><\/small><\/pre>\n\n\n
What if you want to execute the say()<\/code> function repeatedly ten times. In this case, you need to change the hard-coded value 5 in the repeat<\/code> decorator.<\/p>\n\n\n\n
However, this solution isn’t flexible. For example, you want to use the repeat<\/code> decorator to execute a function 5 times and another 10 times. The repeat<\/code> decorator would not meet the requirement.<\/p>\n\n\n\n
To fix this, you need to change the repeat<\/code> decorator so that it accepts an argument that specifies the number of times a function should execute like this:<\/p>\n\n\n
@repeat(5)<\/span>\ndef<\/span> say<\/span>(message)<\/span>:<\/span>\n    ...\n<\/code><\/span>Code language:<\/span> Python<\/span> (<\/span>python<\/span>)<\/span><\/small><\/pre>\n\n\n
To define the repeat<\/code> decorator, the repeat(5)<\/code> should return the original decorator.<\/p>\n\n\n
def<\/span> repeat<\/span>(times)<\/span>:<\/span>\n    # return the original \"repeat\" decorator<\/span>\n<\/code><\/span>Code language:<\/span> Python<\/span> (<\/span>python<\/span>)<\/span><\/small><\/pre>\n\n\n
The new repeat<\/code> function returns a decorator. And it’s often referred to as a decorator factory.<\/p>\n\n\n\n
The following repeat<\/code> function returns a decorator:<\/p>\n\n\n
def<\/span> repeat<\/span>(times)<\/span>:<\/span>\n    ''' call a function a number of times '''<\/span>\n    def<\/span> decorate<\/span>(fn)<\/span>:<\/span>\n        @wraps(fn)<\/span>\n        def<\/span> wrapper<\/span>(*args, **kwargs)<\/span>:<\/span>\n            for<\/span> _ in<\/span> range(times):\n                result = fn(*args, **kwargs)\n            return<\/span> result\n        return<\/span> wrapper\n    return<\/span> decorate\n<\/code><\/span>Code language:<\/span> Python<\/span> (<\/span>python<\/span>)<\/span><\/small><\/pre>\n\n\n
In this code, the decorate<\/code> function is a decorator. It’s equivalent to the original repeat<\/code> decorator.<\/p>\n\n\n\n
Note that the new repeat function isn’t a decorator. It’s a decorator factory that returns a decorator.<\/p>\n\n\n\n
Put it all together.<\/p>\n\n\n
from<\/span> functools import<\/span> wraps\n\n\ndef<\/span> repeat<\/span>(times)<\/span>:<\/span>\n    ''' call a function a number of times '''<\/span>\n    def<\/span> decorate<\/span>(fn)<\/span>:<\/span>\n        @wraps(fn)<\/span>\n        def<\/span> wrapper<\/span>(*args, **kwargs)<\/span>:<\/span>\n            for<\/span> _ in<\/span> range(times):\n                result = fn(*args, **kwargs)\n            return<\/span> result\n        return<\/span> wrapper\n    return<\/span> decorate\n\n\n@repeat(10)<\/span>\ndef<\/span> say<\/span>(message)<\/span>:<\/span>\n    ''' print the message \n    Arguments\n        message: the message to show\n    '''<\/span>\n    print(message)\n\n\nsay('Hello'<\/span>)\n<\/code><\/span>Code language:<\/span> Python<\/span> (<\/span>python<\/span>)<\/span><\/small><\/pre>\n\n\n
Output:<\/p>\n\n\n
Hello\nHello\nHello\nHello\nHello\nHello\nHello\nHello\nHello\nHello<\/code><\/span>Code language:<\/span> plaintext<\/span> (<\/span>plaintext<\/span>)<\/span><\/small><\/pre>\n\n\n
Summary #<\/a><\/h2>\n\n\n\n
    \n
  • Use a factory decorator to return a decorator that accepts arguments.<\/li>\n<\/ul>\n
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Try it<\/a><\/p>\n\n\n\n
Try it<\/a><\/p>\n\n\n\n