Python decorator class method self

Python decorator class method self

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In Python, a decorator is a small function that takes another function as an argument and returns a new function that "wraps" the original function. The purpose of decorators is to modify or extend the behavior of the original function without permanently changing it.

One common use case for decorators is to log information about the execution of a function. For example, you might want to record how long each function takes to run, what arguments were passed in, and what output was produced.

Here's an example of how you can create a decorator that logs this kind of information:

import functools
import time
def timer(func):
@functools.wraps(func)
def wrapper(*args, **kwargs):
start_time = time.time()
result = func(*args, **kwargs)
end_time = time.time()
print(f"Function '{func.name}' took {end_time - start_time:.2f} seconds to run.")
return result
return wrapper
@timer
def add(a, b):
return a + b
print(add(2, 3))  # Output: Function 'add' took 0.00 seconds to run.

In this example, the timer decorator takes the original add function as an argument and returns a new function wrapper. The wrapper function calls the original add function with the given arguments and then logs some information about how long it took to run.

To apply the decorator to the original add function, we use the @ symbol before the timer decorator. This is called "decorating" the function. The result is that when you call add(2, 3), you'll see a message printed out with the execution time of the function.

As for class methods and self, in Python, every instance method (i.e., a method that belongs to an instance of a class) has access to its own self parameter. The self parameter refers to the instance itself.

Here's an example:

class Person:
def init(self, name):
self.name = name
def greet(self):
print(f"Hello, my name is {self.name}!")
person = Person("John")
person.greet()  # Output: Hello, my name is John!

In this example, the greet method belongs to the instance of the Person class. The self parameter refers to that instance. When you call person.greet(), it prints out a greeting message with the person's name.

Class methods are similar to instance methods, but they belong to the class itself rather than an instance of the class. Class methods don't have access to the self parameter by default. However, you can pass in the class as an argument using the cls keyword:

class Person:
def init(cls, name):
cls.name = name
@classmethod
def greet(cls):
print(f"Greetings from {cls.name}!")
Person.greet()  # Output: Greetings from None!
person = Person("John")
person.greet()  # Output: AttributeError: 'Person' object has no attribute 'name'

In this example, the greet class method belongs to the Person class itself. The cls parameter refers to the class. However, when you call person.greet(), it raises an error because instance methods don't have access to the class's attributes.

Python decorator class method example

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