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 python2.5

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#!/usr/bin/env python

# -*- coding: utf-8 -*-

#

# Based on AboutNil in the Ruby Koans

#

from runner.koan import *

class AboutNone(Koan):

def test_none_is_an_object(self):

"Unlike NULL in a lot of languages"

self.assertEqual(__, isinstance(None, object))

def test_none_is_universal(self):

"There is only one None"

self.assertEqual(__, None is None)

def test_what_exception_do_you_get_when_calling_nonexistent_methods_on_None(self):

"""

What is the Exception that is thrown when you call a method that does

not exist?

Hint: launch python command console and try the code in the block below.

Don't worry about what 'try' and 'catch' do, we'll talk about this later

"""

try:

None.some_method_none_does_not_know_about()

except Exception, ex:

# What exception has been caught?

self.assertEqual(__, ex.__class__.__name__)

# What message was attached to the exception?

# (HINT: replace __ with part of the error message.)

self.assertMatch(__, ex.args[0])

def test_none_is_distinct(self):

"""

None is distinct from other things which are False.

"""

self.assertEqual(____, None is not 0)

self.assertEqual(____, None is not False)