Code snippets for Decorators and Descriptors Decoded

Functions as objects



In [ ]:

    
fruit = ['banana', 'grapefruit', 'lime', 'pineapple']
sorted(fruit, key=len)



In [ ]:

    
def fibonacci(n:int) -> int:
    '''returns the nth Fibonacci number'''
    a, b = 0, 1
    while n > 0:
        a, b = b, a + b
        n -= 1
    return a



In [ ]:

    
[fibonacci(n) for n in range(12)]



In [ ]:

    
# ?fibonacci



In [ ]:

    
fibonacci.__doc__



In [ ]:

    
fibonacci.__annotations__



In [ ]:

    
fibonacci.__code__.co_varnames



In [ ]:

    
from inspect import signature
signature(fibonacci).parameters

Decorators 101

Decorators are syntactic sugar



In [ ]:

    
def square(n):
    return n * n

square(3)



In [ ]:

    
from decolib import floatify



In [ ]:

    
@floatify
def square(n):
    return n * n

square(3)



In [ ]:

    
square



In [ ]:

    
??square

Decorators may replace the decorated function



In [ ]:

    
def deco(f):
    def inner():
        return 'inner result'
    return inner

@deco
def target():
    return 'original result'
    
target()



In [ ]:

    
target



In [ ]:

    
def double(n):
    return n * 2

double(4)



In [ ]:

    
blessed = []

def bless(f):
    blessed.append(f)
    return f  # Important: return a function!



In [ ]:

    
def double(n):
    return n * 2



In [ ]:

    
bless(double)



In [ ]:

    
@bless
def triple(n):
    return n * 3



In [ ]:

    
blessed



In [ ]:

    
def triple(n):
    return n * 3

triple = bless(triple)



In [ ]:

    
def square(n):
    return n * n



In [ ]:

    
square(3)



In [ ]:

    
square

functools.wraps



In [1]:

    
from decolib2 import floatify

@floatify
def square(n):
    """returns n squared"""
    return n * n

square(3)









    Out[1]:





9.0



In [2]:

    
square









    Out[2]:





<function __main__.square>



In [3]:

    
help(square)









    



Help on function square in module __main__:

square(n)
    returns n squared



In [4]:

    
??square



In [ ]: