.. getthecode:: decorators.py
    :language: python3
    :hidden:

============
 Decorators
============

This page contains a memo on decorators.


.. code-block:: py3

    from Tools import *
    

Function Decorators
-------------------

`PEP 318 -- Decorators for Functions and Methods <https://www.python.org/dev/peps/pep-0318>`_


.. code-block:: py3

    def func_decorator_1(func):
        print_function('func_decorator_1', func)
        # do something with func
        # func.attribute = ...
        return func
    
    def func_decorator_2(func):
        print_function('func_decorator_2', func)
        return func
    
    # Same as foo = func_decorator_2(func_decorator_1(foo))
    @func_decorator_2
    @func_decorator_1
    def foo():
      pass
    

.. code-block:: none

    @func_decorator_1
        <function foo at 0x7f86ac60a7b8>
    @func_decorator_2
        <function foo at 0x7f86ac60a7b8>
    

.. code-block:: py3

    class func_decorator_3:
    
        def __init__(self, *args, **kwargs):
            print_method(self, '__init__', args, kwargs)
    
        def __call__(self, func):
            print_method(self, '__call__', func)
            return func
    
    # Same as foo = func_decorator_3(*args, **kwargs)(foo)
    @func_decorator_3(1, 2, attr1='abc')
    def foo():
      pass
    

.. code-block:: none

    @func_decorator_3.__init__
        (1, 2)
        {'attr1': 'abc'}
    @func_decorator_3.__call__
        <function foo at 0x7f86ac5a4ea0>
    

Class Decorators
----------------

`PEP 3129 -- Class Decorators <https://www.python.org/dev/peps/pep-3129>`_


.. code-block:: py3

    def class_decorator_1(cls):
        print_function('class_decorator_1', cls)
        # cls.attribute = ...
        return cls
    
    def class_decorator_2(cls):
        print_function('class_decorator_2', cls)
        return cls
    
    # Same as A = class_decorator_2(class_decorator_1(A))
    @class_decorator_2
    @class_decorator_1
    class A:
      pass
    

.. code-block:: none

    @class_decorator_1
        <class '__main__.A'>
    @class_decorator_2
        <class '__main__.A'>