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@TutorialDoctor
Last active January 7, 2019 10:29
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Tutorial Code for Python Decorators
# A decorator is a function that takes a function as an argument and adds a bow tie on top of it.
def decorator(func):
return func
#This "decorator" doesn't really decorate the input function. It just returns the input function.
@decorator
def aFunc():
print('hello\n')
aFunc()
#The decorator above doesn't have a bow tie. Let's create a decorator that can decorate an input function with a bowtie.
def decorate_with_bowtie(func):
print('>-<')
#This bow tie could be whatever logic you want it to be. The key is that the bow tie code is executed "before" (on top of) the input-function.
return func
@decorate_with_bowtie
def aFunc2():
print('I am decorated with a bow tie')
aFunc2()
#I can decorate multiple functions with a bow tie now
@decorate_with_bowtie
def aFunc3():
print('I am decorated with a bow tie also')
aFunc3()
# Now we are going to wrap the input function and add a bow tie to it
def wrap_and_tie(func):
def wrapped():
#Bow tie
print('>-<')
#Call the function
func()
print('..Your function has been wrapped and bow-tied')
#Return the wrapped function
return wrapped
@wrap_and_tie
def aFunc4():
print('gift')
aFunc4()
#Decorate a divide function with a check for a valid denominator value.
def prevent_divide_by_zero(func):
#To pass the arguments of the function to the wrapper:
def wrapped(*args,**kwargs):
#If the 2nd argument is not 0:
if args[1]!=0:
print("The quotient is:")
#Call the input-function, passing in the keyword arguments
func(*args,**kwargs)
#Otherwise print that they cannot divide by zero.
else:
print("Can't divide by 0")
#Return the wrapped function
return wrapped
@prevent_divide_by_zero
def divide(a,b):
print(a/b)
divide(20,0)
divide(20,6.0)
#Now for something more useful. Decorate an attempt to create a user with a user validation
def validate_user(func):
def wrapped(*args,**kwargs):
#If the username argument is 'admin' and the password argument is 'password':
if kwargs['username']=='admin' and kwargs['password']=='password':
print('ACCESS GRANTED: \n{}'.format(kwargs))
#execute the input-function
func()
#No arguments needed because the arguments have default values.
#Otherwise:
else:
#Not needed, but first, print the keyword arguments entered
print(kwargs)
print('This user does not have administrative privilages.')
print('ACCESS DENIED')
#and return the nicely wrapped function.
return wrapped
@validate_user
def create_user(username="admin",password="password"):
response = {'msg':"User created successfully","User":{"username":username,"password":password}}
print(response)
print('\n')
create_user(username='joe',password='smith')
print('\n')
create_user(username='admin',password='password')
#-Tutorial Doctor
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