Decorators that take arguments

Writing Functions in Python

Shayne Miel

Software Architect @ Duo Security

def run_three_times(func):
  def wrapper(*args, **kwargs):
    for i in range(3):
      func(*args, **kwargs)
  return wrapper

@run_three_times
def print_sum(a, b):
  print(a + b)

print_sum(3, 5)

8
8
8

run_n_times()

def run_n_times(func):
  def wrapper(*args, **kwargs):
    # How do we pass "n" into this function?
    for i in range(???):
      func(*args, **kwargs)
  return wrapper

@run_n_times(3)
def print_sum(a, b):
  print(a + b)

@run_n_times(5)
def print_hello():
  print('Hello!')

A decorator factory

def run_n_times(n):
  """Define and return a decorator"""

  def decorator(func):

    def wrapper(*args, **kwargs):

      for i in range(n):
        func(*args, **kwargs)

    return wrapper

  return decorator

@run_n_times(3)
def print_sum(a, b):
  print(a + b)

def run_n_times(n):
  """Define and return a decorator"""
  def decorator(func):
    def wrapper(*args, **kwargs):
      for i in range(n):
        func(*args, **kwargs)
    return wrapper
  return decorator

run_three_times = run_n_times(3)

@run_three_times
def print_sum(a, b):
  print(a + b)

@run_n_times(3)
def print_sum(a, b):
  print(a + b)

Using run_n_times()

@run_n_times(3)
def print_sum(a, b):
  print(a + b)

print_sum(3, 5)

8
8
8

@run_n_times(5)
def print_hello():
  print('Hello!')

print_hello()

Hello!
Hello!
Hello!
Hello!
Hello!

Let's practice!

Writing Functions in Python