FQN Decorators

Installation

At the command line::

$ pip install fqn-decorators

Usage

import fqn_decorators.decorators

Introduction

By extending the Decorator class you can create simple decorators. Implement the Decorator.before and/or Decorator.after methods to perform actions before or after execution of the decorated item. The Decorator.before method can access the arguments of the decorated item by changing the Decorator.args and Decorator.kwargs attributes. The Decorator.after method can access or change the result using the Decorator.result attribute. The Decorator.exception method can be used for do something with an Exception that has been raised. In all three methods the Decorator.fqn and Decorator.func attributes are available.

Simple decorator

Create a simple decorator:

import fqn_decorators
import time

class time_it(fqn_decorators.Decorator):

    def before(self):
        self.start = time.time()

    def after(self):
        duration = time.time() - self.start
        print("{0} took {1} seconds".format(self.fqn, duration))


@time_it
def my_function():
    time.sleep(1)

my_function()
# __main__.my_function took 1.00293397903 seconds

Decorator with arguments

It is also very easy to create a decorator with arguments. It is not possible to create decorators with non-keyworded arguments.

Example:

import fqn_decorators
import time

class threshold(fqn_decorators.Decorator):

    def before(self):
        self.start = time.time()

    def after(self):
        duration = time.time() - self.start
        treshold = self.params.get('threshold')
        if threshold and duration > threshold:
            raise Exception('Execution took longer than the threshold')


@threshold(threshold=2)
def my_function():
    time.sleep(3)

my_function()
# Exception: Execution took longer than the threshold

Async Decorator

There's also support for decorating coroutines (or any awaitable), for Python >=3.5 only.

The implementation is the same as with the sync version, just inherit from fqn_decorators.asynchronous.AsyncDecorator instead.

Example:

import asyncio
import time
from fqn_decorators.asynchronous import AsyncDecorator

class time_it_async(AsyncDecorator):

    def before(self):
        self.start = time.time()

    def after(self):
        duration = time.time() - self.start
        print("{0} took {1} seconds".format(self.fqn, duration))

@time_it_async
async def coro():
    await asyncio.sleep(1)

asyncio.run(coro())
# __main__.coro took 1.001493215560913 seconds