Niels Notes

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

Decorators extend functions, methods, classes without explicitly modifying the code of the item being decorated. 

example of a decorator //Italic (skelleton structure only)//:

<code python>
def decorator_function(func):
    ''' Receives the function being decorated as first argument'''
    
    def actual_decorator(*args, **kwargs): 
        '''function that actually performs the decorated logic '''
        
        # do something, before original logic
                
        #call the original function        
        func(*args,**kwargs)
        
        # and/or do something after. 
        
        #return result 
    
    #return the actual decorator so it gets called by calling context . 
    return actual_decorator   

</code>

example of decorator with arguments//Italic (skelleton structure only)//:

<code python>
def decorator_function(a, b):
    ''' Receives the decorator arguments'''
    
    def additional_wrapper(func):
        ''' receivs the function (and its arguments) being decorated '''
    
        def actual_decorator(*args, **kwargs): 
            '''function that actually performs the decorated logic '''
            
            #arguments a and b passed from outer fuction are in scope but read only. 
               if a > b:
                   pass         
            # do something, before original logic                      
            
            #call the original function            
            func(*args,**kwargs)
            
            # and/or do something after. 
            
            #return result
        
        # return function to calling context (so that it gets executed).    
        return actual_decorator   

    #return fuction to calling context (so that it gets executed).
    return additional_wrapper
</code>


**Related:**
  *[[https://peps.python.org/pep-0318/ | PEP 318 – Decorators for Functions and Methods ]]
  *[[https://pybit.es/articles/decorators-by-example/ | Learning Python Decorators by Example (pybit.es)]]
  *[[https://wiki.python.org/moin/PythonDecorators| PythonDecorators (wiki.python.org)]]
  *[[https://builtin.com/software-engineering-perspectives/python-class-decorator| Using Python Class Decorators (builtin.com)]]
  *[[https://realpython.com/python-metaclasses/| Python Metaclasses (realpython.com)]]((With metaclasses you can define how classes are created.))
  *[[https://realpython.com/primer-on-python-decorators/| Primer on Python decorators (realpython.com)]]
  *[[https://python-reference.readthedocs.io/en/latest/docs/functions/property.html | article on property decorator]]
   

{{tag>python development decorators}}
Niels Notes

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