Question

I have written a chainable API (in a similar style to jQuery) as follows:

class ChainableAPI:
  def show(self):
    self.visibility = 1
    return self

  def goBlue(self):
    self.color = 'Blue'
    return self

  def die(self):
    self.life = 0
    return self

chainableAPI = ChainableAPI()

(chainableAPI
  .goBlue()
  .show()
  .die()
  .goBlue())

Notice how each method of ChainableAPI ends with return self. Is there a way to have all methods to return self automatically? That way I do not have to specify return self manually for each method.

Answer 1

You could use a decorator:

import functools

def chainable(func):
    @functools.wraps(func)
    def decorated(*args, **kwargs):
        func(*args, **kwargs)
        return args[0]
    return decorated

Then the class would look like this:

class Foo(object):
    @chainable
    def show(self):
        self.visibility = True

    @chainable
    def go_blue(self):
        self.color = 'blue'

But is it better than just writing return self?

Also, a class decorator could be written to apply the chainable decorator to all methods not starting with _:

def all_chainable(klass):
    for k, v in klass.__dict__.items():
        if not k.startswith('_') and callable(v):
            setattr(klass, k, chainable(v))
    return klass

Example:

@all_chainable
class Foo(object):
    def show(self):
        self.visibility = True

Still, no matter how cool it may be I still think you should just use return self. But this shows how powerfull Python is.