python-duck-typing

• Python code style that encourages you to care about what an object is capable of rather than what it is
• As in, if it walks like a duck and quacks like a duck, for all intents and purposes, it’s a duck
• So, don’t care about the type; care about the behavior (its traits)
  • Can it quack?
  • Can it fly?
  • Instead of “is it a duck?”
• Is this in opposition to static typing (which defines what things are)?
• Does not mean LBYL by checking if it can quack/fly (e.g. if hasattr(thing, 'quack'))
• Instead, just try to make it quack and handle failure if it occurs

def quack_and_fly(thing):
    try:
        thing.quack()
        thing.fly()
    except AttributeError as e:
        print(e)

• Relationship to EAFP (python coding style of preferring to try/except as opposed to checking preconditions)
• Relationship to protocols (allows static typing and duck typing to work together): Protocols — typing documentation
• Python Tutorial: Duck Typing and Asking Forgiveness, Not Permission (EAFP) - YouTube - Corey Schafer