Forwardable as in Ruby's stdlib
Project description
Utility for easy object composition via delegation. Roughly ported from Ruby’s forwardable standard library.
Requirements
Python 2.7 or 3.3 w/ standard library. Might work on other version of Python, too.
Installation
$ pip install forwardable
Usage
Most Common Use Case
The @forwardable.forwardable() decorator enables you to use def_delegator() and def_delegators() in a class definition block.
Use def_delegators() to define multiple attr forwarding:
from forwardable import forwardable
@forwardable() # Note the () here, which is required.
class Foo(object):
def_delegators('bar', ('add', '__len__'))
def __init__(self):
self.bar = set()
foo = Foo()
foo.add(1) # Delegates to foo.bar.add()
assert len(foo) == 1 # Magic methods works, too
Easy, heh?
Define a Single Forwarding
In case you only need to delegate one method to a delegatee, just use def_delegator:
from forwardable import forwardable
@forwardable()
class Foo(object):
def_delegator('bar', '__len__')
def __init__(self):
self.bar = set()
assert len(Foo()) == 0
And it should work just fine. Actually, def_delegators() calls def_delegator() under the hood.
Plucking
from forwardable import forwardable
@forwardable()
class MyDict(object):
def_delegator('dct.get', '__call__')
def __init__(self):
self.dct = {'foo', 42}
d = MyDict()
# Equivlant to d.dct.get('foo')
assert d('foo') == 42
Less Magical Usage
The @forwardable() decorator injects def_delegator{,s} into the module scope temorarily, which is why you don’t have to import them explicitly. This is admittedly magical but discourages the usage of import *. And it’s always nice to type less characters whenever unnecessary.
If you hesitate to utilize this injection magic, just explicitly say from forwardable import def_delegator, def_delegators, use them in a class definition and you’ll be fine.
Links
Source Repository: https://github.com/5long/forwardable
License
MIT license.
Project details
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