logo
Tags down

shadow

how to make a decorator function to be part of class


By : Miriam Mugauri
Date : October 16 2020, 06:10 PM
will help you You can't use a decorator on a method where the decorator expression refers to an instance attribute. That's because decorators are executed when the function they decorate is being created. Inside a class statement body that means that when decorators are applied, there is no class yet, and without a class, there can't be any instances either.
You have two options:
code :
class Websocket:

    def __init__(self):
        self.eio = engineio.Client()
        self.eio.connect('http://localhost:5000')
        self.eio.on('connect', self.on_connect)
        # don't call wait, see below

    def on_connect(self):
        print('connection established')
class Websocket:

    def __init__(self):
        self.eio = engineio.Client()
        self.eio.connect('http://localhost:5000')

        @self.eio.on('connect')
        def on_connect():
            print('connection established')

        # don't call wait, see below


but that makes it much harder to use that function directly from other code. 
class Websocket:
    def __init__(self, socket_url):
        self.eio = engineio.Client()
        self.eio.connect(socket_url)
        self.eio.on('connect', self.on_connect)
        # other registrations

    def on_connect(self):
        # handle connection

    # other handlers

    def wait(self):
        self.eio.wait()

websocket = Websocket('http://localhost:5000)
websocket.wait()


Share : facebook icon twitter icon

How to use Python Decorator to change only one part of function?


By : Hiesham Merhi
Date : March 29 2020, 07:55 AM
hop of those help? What do you think about using a separate function (as a private method) for list processing? For example, you may do the following:
code :
def __list_processing(self, list): 
    #do the generic processing of your lists

def list_expenses(self):
    #invoke __list_processing with self.expensedict as a parameter

def list_income(self):
    #invoke __list_processing with self.incomedict as a parameter

typescript class decorator: typing properties defined in decorator function


By : Daniel Toney
Date : March 29 2020, 07:55 AM
I hope this helps . Within the decorator target refers to the function—Foo—rather than the prototype—Foo.prototype.
So in the decorator doing target.inDecorator = ... is the same as Foo.inDecorator = ... and not Foo.prototype.inDecorator = ....
code :
interface BarStatic {
    new(): BarInstance;
    inDecorator: string;
}

interface BarInstance {
    inDecorator: string;
}

function bar(target: BarStatic) {
    target.inDecorator = 'static';
    // note that prototype will be `any` here though
    target.prototype.inDecorator = 'instance';
}

@bar
class Foo {
    static inDecorator: string; // required
    inDecorator: string;        // required
    inClass: string;

    constructor() {
        this.inClass = 'a string';
    }

    getInClass() {
        return this.inClass;
    }
}

console.log(Foo.inDecorator);           // static
console.log(Foo.prototype.inDecorator); // instance
const foo = new Foo();
console.log(foo.getInClass());          // a string
console.log(foo.inDecorator);           // instance

typescript class decorator can not access static value if decorator return as high order function


By : J. Ortega
Date : March 29 2020, 07:55 AM
To fix the issue you can do The way decorators work is that if you return a value from the decorator, that will replace the decorated class. The function you return can successfully replace Foo but since it does not inherit the properties of the original Foo it will not be available on the replaced Foo.
The simplest solution is to return an anonymous class that derives from the class that is passed to the decorator.
code :
function Bar(FooClass: typeof Foo) {
    console.log('in Bar decorator');
    return class extends FooClass {
        constructor(args: any) {
            super(args);
            console.log('in Bar high order function: ', args);
        }
    };
}

@Bar
class Foo {

    a = 1;
    static b = 2;
    constructor(args: any) {
        console.log('in Foo constructor')
        console.log('Foo instance a: ', this.a);
        console.log('Foo static b: ', Foo.b);
    }
}

new Foo(123);

How can I make a class decorator not break isinstance function?


By : user2577323
Date : March 29 2020, 07:55 AM
hope this fix your issue You can use the singleton class decorator in the Python Decorator Library.
It works because it modifies the existing class (replaces the __new__() method) instead of replacing it with a completely separate class as is being done in the code in your question.
code :
import functools

# from https://wiki.python.org/moin/PythonDecoratorLibrary#Singleton
def singleton(cls):
    ''' Use class as singleton. '''

    cls.__new_original__ = cls.__new__

    @functools.wraps(cls.__new__)
    def singleton_new(cls, *args, **kw):
        it =  cls.__dict__.get('__it__')
        if it is not None:
            return it

        cls.__it__ = it = cls.__new_original__(cls, *args, **kw)
        it.__init_original__(*args, **kw)
        return it

    cls.__new__ = singleton_new
    cls.__init_original__ = cls.__init__
    cls.__init__ = object.__init__

    return cls
[2, 3, 4, 5, 6, 0, 1, 2, 3, 4]
[5, 6, 0, 1, 2]
[3, 4, 5, 6, 0, 1, 2]
<class '__main__.Counter'>
<class '__main__.Counter'>
True

Limit of decorator as class compared to decorator as function


By : Sylar
Date : March 29 2020, 07:55 AM
like below fixes the issue I want to make sure that I understood correctly how decorator as class works. , You could write an equivalent class-based decorator like this...
code :
class addx:
    def __new__(self, obj):
        obj.x = 10
        return obj

@addx
class A:
    pass

assert A.x == 10
def addx_func(kls):
    def wrapper():
        res = kls()
        res.x = 10
        return res

    return wrapper


class addx_class:
    def __init__(self, kls):
        self.kls = kls

    def __call__(self):
        res = self.kls()
        res.x = 10
        return res


@addx_func
class A:
    pass


@addx_class
class B:
    pass


a = A()
assert a.x == 10

b = B()
assert b.x == 10
Related Posts Related Posts :
  • Setting debug = False makes the Django app crash with the following error, how to fix it?
  • How to get the average of many lists embedded within each other?
  • Paramiko with subprocess
  • 2D table conversion for example: y = f(x1,x2) => x1 = f(y, x2)
  • Return a literal string of a tuple in python
  • How to split a Column when you have same values?
  • How to perform str.strip in dataframe and save it with inplace=true?
  • why zip(*k) can't work when k is a iterator?
  • How to get list as an input from command line python?
  • Is Tensorflow Dataset.from_generator deprecated in tensorflow 2.0 ? It throws tf.py_func deprecation error
  • Loop as long as input is greater then previous input
  • How to combine 2 rows based on different column values
  • Extracting 3 levels deep product details. Getting error NameError: name 'item' is not defined
  • How do I get the default fill values?
  • How to convert single list's elements in form of dictionary
  • Search a user given number inside a list using for loop
  • How to extract a particular value from this data structure?
  • How to save a df into two excel files in multiple locations?
  • How to get the sum of a field in Django
  • i+ =1 generating a Syntax error in for loop
  • Lookup if Dictionary key contains items in Python
  • How to comma separate an array of integers in python?
  • Extract rows from pandas dataframe corresponding to list of month-day
  • Reading formatted array from file in Python
  • Python Error: can't install scipy.optimize.brentq
  • Why isn't my gradient descent algorithm working?
  • How to find a 'str' in a 2-D array and return element in next column?
  • Code not outputting a value in hackerrank
  • Fibonacci sequence calculator seems correct but can't find similar code online. Is there something wrong?
  • Can't call attribute of class within the class itself in Python 3.6.5
  • How to make a loop in dictionary to extract values?
  • Is there a way of aggregating rows without summing up their results?
  • I am having a problem with understanding this python code
  • Stop number decrease once 0 reached on dice game - Python
  • Is possible to make a binary search by searching between unknown values?
  • pass object method as function argument for method chaining in python
  • pylint W0622 (Redefining built-in) when overriding "standard" methods in subclasses
  • Extract values from String using Python
  • How do I get a bytearray from a Tkinter entry widget
  • Function not outputing a value in Python
  • Object of type date is not JSON serializable error, while uploading dataframe to bigquery?
  • RegEx for matching specific element of HTML
  • How to initiate widgets through tk/tcl
  • urlparse does not raise exception for an invalid url
  • plot stacked percentage barchart matplotlib
  • How to have the .isupper() and .islower() methods in one line of code?
  • Removing header index from dataframe
  • how to input all data first, then give all output in python?
  • Hot to fix Tensorflow model not running in Eager mode with .fit()?
  • Proxy configuration in Scrapy
  • If/else statement within loop over dataframe
  • I have a code or stop the loop, I do not know how I can do for what stops
  • python pandas : lambda or other method to count NaN values / len(value)<1 along rows
  • Combine two dataframes with same values in several columns
  • Replace Iterations by elegant Pandas code
  • If all elements match requirement not using "if all"
  • Access to 3D array in fragment shader
  • How to normalize the columns of a DataFrame using sklearn.preprocessing.normalize?
  • Validation loss not moving with MLP in Regression
  • ML with imbalanced binary dataset
  • shadow
    Privacy Policy - Terms - Contact Us © 35dp-dentalpractice.co.uk