Decorators and metadata

Writing Functions in Python

Shayne Miel

Software Architect @ Duo Security

def sleep_n_seconds(n=10):
  """Pause processing for n seconds.

  Args:
    n (int): The number of seconds to pause for.
  """
  time.sleep(n)

print(sleep_n_seconds.__doc__)

Pause processing for n seconds.

  Args:
    n (int): The number of seconds to pause for.

def sleep_n_seconds(n=10):
  """Pause processing for n seconds.

  Args:
    n (int): The number of seconds to pause for.
  """
  time.sleep(n)

print(sleep_n_seconds.__name__)

sleep_n_seconds

print(sleep_n_seconds.__defaults__)

(10,)

@timer
def sleep_n_seconds(n=10):
  """Pause processing for n seconds.

  Args:
    n (int): The number of seconds to pause for.
  """
  time.sleep(n)

print(sleep_n_seconds.__doc__)

print(sleep_n_seconds.__name__)

wrapper

The timer decorator

def timer(func):
  """A decorator that prints how long a function took to run."""

  def wrapper(*args, **kwargs):
    t_start = time.time()

    result = func(*args, **kwargs)

    t_total = time.time() - t_start
    print('{} took {}s'.format(func.__name__, t_total))

    return result

  return wrapper

from functools import wraps

def timer(func):
  """A decorator that prints how long a function took to run."""

  @wraps(func)
  def wrapper(*args, **kwargs):

    t_start = time.time()

    result = func(*args, **kwargs)

    t_total = time.time() - t_start
    print('{} took {}s'.format(func.__name__, t_total))

    return result

  return wrapper

@timer
def sleep_n_seconds(n=10):
  """Pause processing for n seconds.

  Args:
    n (int): The number of seconds to pause for.
  """
  time.sleep(n)

print(sleep_n_seconds.__doc__)

Pause processing for n seconds.

  Args:
    n (int): The number of seconds to pause for.

@timer
def sleep_n_seconds(n=10):
  """Pause processing for n seconds.

  Args:
    n (int): The number of seconds to pause for.
  """
  time.sleep(n)

print(sleep_n_seconds.__name__)

sleep_n_seconds

Access to the original function

@timer
def sleep_n_seconds(n=10):
  """Pause processing for n seconds.

  Args:
    n (int): The number of seconds to pause for.
  """
  time.sleep(n)

sleep_n_seconds.__wrapped__

<function sleep_n_seconds at 0x7f52cab44ae8>

Let's practice!

Writing Functions in Python