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Python decorators for contracts and augmenting OOP.
from distutils.core import setup
The syntax below should be self explanatory. It can be applied both to bound and unbound methods.
# Constraints on passed arguments.
# Constraints can be callables or regular expressions.
# Throws a `AugmentError` by default if contraints are violated.
# Optionally, an error handler can be specified which receives the errors.
@ensure_args(a=(lambda x: x > 10, 'must be greater than 10'),
c=lambda x: x < 5) # `c` will be picked from `kwargs`.
def foo(a, b, **kwargs):
# Ensure at least one of the constraints is true.
@ensure_one_of(a=lambda x: x, b=lambda x: x)
def foo(a, b):
# Ensures only one of the constraints is true.
@ensure_one_of(exclusive=True, c=lambda x: x, d=lambda x: x)
def foo(a, b):
# Transform arguments.
@transform_args(a=lambda x: x * x)
def foo(a):
# Bundling multiple constraints.
# Contracts run in inside out order
# i.e the one right above function will run first.
# In this case, `@ensure_args...` will be the first to run.
@transform_args(a=lambda x: x * x)
@ensure_one_of(c=lambda x: x, d=lambda x: x)
@ensure_args(a=lambda x: x > 10,
b=lambda x: hasattr(x, '__getitem__'),
c=lambda x: x < 5)
def foo(a, b, c=4, d=None):
Function/method hooks.
Basic function hooks to run on entering, leaving or both ways.
def login(root):
print "Logging in."
def logout(root):
print "Logging out"
# `login` will run before entering `home`.
# `logout` will run after exiting from `home`.
# `root` param passed to `home` will be passed to `login`, `logout`.
def home(root):
print "Home page."
def tracer():
print "tracing"
# `tracer` will run both before entering `home` and after
# exiting `home`.
def inbox():
print "Inbox"
Please note that the hooks(`login` and `logout`) above are passed the arguments passed to the wrapped method(`home`).
Method hooks should be accepting the same arguments as wrapped method.
They work the same on bound functions.
class Foo:
def login(self):
print "Logging in."
def logout(self):
print "Logging out"
def home(self, test=None):
print "Home page."
def tracer(self):
print "tracing"
def inbox(self):
print "Inbox"
Dynamic delgation.
class Foo:
def __init__(self):
self.a = 'a'
self.b = 'b'
self.c = 'c'
@delegate_to('foo_delegate', 'a', 'b')
class Bar:
def __init__(self):
self.foo_delegate = Foo()
b = Bar()
# `a` and `b` will be delegated to `Foo`.
print b.a
print b.b
# This will throw an AttributeError.
print b.c
from setuptools import setup
description='Python decorators for contracts and augmenting OOP.',
author='Rahul Kumar',