pyConditions 0.3.0

Commenting sucks so let your code do it for you with Guava like preconditions that also actually do something.

Commenting sucks so let your code do it for you with preconditions that actually do something.

Examples:

from pyconditions.pre import *

@Between( "b", 1, 10 )
def divideAbyB( a, b )
  return a / b

@NotNone( "a" )
@Between( "a", "a", "n" )
@NotNone( "b" )
@Between( "b", "n", "z" )
def concat( a, b ):
  return a + b

@Custom( "a", lambda x: x % 2 == 0 )
@Custom( "b", lambda x: not x % 2 == 0 )
def evenOdd( a, b ):
  return a * b

The documenting is there with the code it self, and if you violate the preconditions then a PyCondition exception is thrown with a much nicer error message than broken code.

evenOdd( 3, 1 )

pyconditions.exceptions.PyCondition: 3 did not pass the custom condition for parameter 'a' in function evenOdd

How about some postconditions?

from pyconditions.post import *

@NotNone()
def test( a ):
  return a

@Custom( lambda a: a % 2 == 0 )
def even( a ):
  return a

test( None )

pyconditions.exception.PyCondition: The return value for uber.awesome.project.test was None

You can also mix the two as well.

from pyconditions import pre
from pyconditions import post

@pre.Custom( "a", lamda a: a % 2 == 0 )
@post.Custom( lambda a: a % 2 == 0 )
def superSafeEven( a ):
  return a

Want some class invariant shenanigans?

from pyconditions.invariant import Invariant, FieldsNotNone
@FieldsNotNone( [ "test" ] )
class Test:
    def __init__( self ):
            self.test = 1
    def add( self ):
            return self.test + 1
    def set( self, v ):
            self.test = v

t = Test()
print t.add()
t.set( None )

That last call to add will cause the invariant to fail and thus throw the following:

pyconditions.exceptions.PyCondition: Field "test" was None when it should not have been in invariant "notNone"

Have conditions you want added? Open a PR with code.

Have an issue? Open a PR with fixed code.