lquenti / nchainz

Like 2 Chainz, but for any length

About the Archivation

It still works, I just don't plan to update it anymore. I also released into the public domain, so feel free to do whatever with it.

nchainz - Automatic Method Chaining in Python

A metaclass for automatic method chaining. (Only for methods that return None, obviously)

from nchainz import Chainz

class A(metaclass=Chainz):

  def has_return_value(self):
    return 4

  def this_is_chainable(self):
    print("hello")
    # implicitly returns self

a = A()
assert a is a.this_is_chainable().this_is_chainable()
assert a.has_return_value() == 4

What is Method Chaining?

Method chaining describes the Syntax of not having to assign objects between methods which are changing the state.

For example, in JS one can just chain the array transformations like

[1,2,3,4,5,6].filter(x => x % 2 == 0).map(x => x * x).find(x => x > 30)

How to do it manually?

Pretty easy. You just return self. Here is an example:

class MyNum:
  def __init__(self, x):
    self.x = x
  def inc(self):
    self.x += 1
    return self

three = MyNum(3)
six = three.inc().inc().inc()
assert three.x+3 == six.x

Install

pip install nchainz

Use

Just use the Chainz metaclass:

from nchainz import Chainz

class MyClass(metaclass=Chainz):
  ...

Why? Like seriously, Why?

I had my 5 minutes, I am sorry.

Further reading

It's such a great read, you should really read it. (Written for Python 2)

Meta-classes Made Easy