pyConditions 0.0.3

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

Guava like precondition enforcing for Python.

Has been tested against:

• 2.6

• 2.7

• 3.2

• 3.3

• pypy

Decorate functions with preconditions so that your code documents itself and at the same time removes the boilerplate code that is typically required when checking parameters.

An Example:

def divideAby1or10( a, b ):
    if not ( 1 <= b <= 10 ):
        <raise some error>
    else:
        return a / b

Simply becomes the following:

from pyconditions.pre import Pre
pre = Pre()

@pre.between( "b", 1, 10 )
def divideAbyB( a, b )
  return a / b

In the above example the precondition pre.between ensures that the b variable is between (1, 10) inclusive. If it is not then a PyCondition exception is thrown with the error message detailing what went wrong.

More Examples:

def divideAby1or10( a, b ):
    if not ( 1 <= b <= 10 ):
        <raise some error>
    else:
        return a / b

Simply becomes the following:

from pyconditions.pre import Between

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

In the above example the precondition pre.between ensures that the b variable is between (1, 10) inclusive. If it is not then a PyCondition exception is thrown with the error message detailing what went wrong.

More Examples:

from pyconditions.pre import Between, NotNone
pre = Pre()

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

The above ensures that the variables a and b are never None and that a is between ( ?a?, ?n? ) inclusively and b is between ( ?n?, ?z? ) inclusively.

from pyconditions.pre import Custom

BASES = [ 2, 3, 4 ]

@Custom( a, lambda x: x in BASES )
@Custom( b, lambda x: x % 2 == 0 )
def weirdMethod( a, b ):
    return a ** b

Using the custom precondition you are able to pass in any function that receives a single parameter and perform whatever condition checking you need.