README.md

Built-ins and libraries

functools

The functools module provides some useful tools for functions, including several decorators.

• @wraps

  @wraps is useful when creating decorators. It updates the new function to "look like" the original function.

  (Script available)

  from functools import wraps
  
  def decorator(func):
      @wraps(func)
      def __new_func(*args, **kwargs):
          # do stuff
          return func(*args, **kwargs)
  
      return __new_func
  
  @decorator
  def f():
      """
      This is f!
      :return:
      """
      pass
  
  if __name__ == '__main__':
      help(f)  # try removing the @wraps decorator

• @lru_cache

  @lru_cache lets a function memorize its previous calls and their results, eliminating the need to make repetitive calculations.

  (Script available)

  import sys
  import time
  
  from functools import lru_cache
  
  @lru_cache()
  def fibonacci(n):
      print("Calculating {}".format(n), file=sys.stderr)
      time.sleep(0.1)
      if n <= 0:
          return 0
      if n == 1:
          return 1
      return fibonacci(n - 1) + fibonacci(n - 2)
  
  if __name__ == '__main__':
      print(fibonacci(10))
      print(fibonacci(20))

  There is also the "lru" aspect of the tool, which has a more detailed explanation in the docs.

• @total_ordering

  Doc:

  Given a class defining one or more rich comparison ordering methods, this class decorator supplies the rest. This simplifies the effort involved in specifying all of the possible rich comparison operations:

  The class must define one of __lt__(), __le__(), __gt__(), or __ge__(). In addition, the class should supply an __eq__() method.

  (Script available)

  from functools import total_ordering
  
  @total_ordering
  class Integer(object):
      def __init__(self, x):
          self.x = x
  
      def __eq__(self, other):
          return self.x == other.x
  
      def __lt__(self, other):
          return self.x < other.x
  
  if __name__ == '__main__':
      print(Integer(1) >= Integer(2))  # try removing @total_ordering decorator

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