Flask-Augment 0.5

Flask-Augment is a Python utility for contract-based programming and method hooks.

Installation

pip install augment

Examples

Contracts.

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 `TypeError` by default if contraints are violated.
# Optionally, an error handler can be specified which receives the errors.
@ensure_args(a=lambda x: x > 10,
 b=r'^?-\d+(\.\d+)$',
 c=lambda x: x < 5) # `c` will be picked from `kwargs`.
def foo(a, b, **kwargs):
 pass

# Ensure at least one of the constraints is true.
@ensure_one_of(a=lambda x: x, b=lambda x: x)
def foo(a, b):
 pass

# 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):
 pass

# Transform arguments.
@transform_args(a=lambda x: x * x)
def foo(a):
 pass

# Bundling multiple constraints.
# Contracts run in top down order
# i.e the top most will run first.
# In this case, `@transform_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):
 pass

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`.
@enter(login)
@leave(logout)
def home(root):
 print "Home page."


def tracer():
 print "tracing"

# `tracer` will run both before entering `home` and after
# exiting `home`.
@around(tracer)
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"

 @leave(logout)
 @enter(login)
 def home(self, test=None):
 print "Home page."

 def tracer(self):
 print "tracing"

 @around(tracer)
 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


Product's homepage

Requirements:

· Python
· Flask