iframe-proxy | Sunbelt Computer Software

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#!/usr/bin/env python
# -*- coding: utf-8 -*-
# Partially based on AboutMessagePassing in the Ruby Koans
from runner.koan import *
class AboutAttributeAccess(Koan):
    class TypicalObject(object):
        pass
    def test_calling_undefined_functions_normally_results_in_errors(self):
        typical = self.TypicalObject()
        try:
            typical.foobar()
        except Exception as exception:
            self.assertEqual(__, exception.__class__.__name__)
            self.assertMatch(__, exception[0])
    def test_calling_getattribute_causes_an_attribute_error(self):
        typical = self.TypicalObject()
        try:
            typical.__getattribute__('foobar')
        except AttributeError as exception:
            self.assertMatch(__, exception[0])
        # THINK ABOUT IT:
        # If the method __getattribute__() causes the AttributeError, then
        # what would happen if we redefine __getattribute__()?
    # ------------------------------------------------------------------
    class CatchAllAttributeReads(object):
        def __getattribute__(self, attr_name):
            return "Someone called '" + attr_name + \
                "' and it could not be found"
    def test_all_attribute_reads_are_caught(self):
        catcher = self.CatchAllAttributeReads()
        self.assertMatch(__, catcher.foobar)
    def test_intercepting_return_values_can_disrupt_the_call_chain(self):
        catcher = self.CatchAllAttributeReads()
        self.assertMatch(__, catcher.foobaz)  # This is fine
        try:
            catcher.foobaz(1)
        except TypeError as ex:
            self.assertMatch(__, ex[0])
        # foobaz returns a string. What happens to the '(1)' part?
        # Try entering this into a python console to reproduce the issue:
        #     "foobaz"(1)
    def test_changing_getattribute_will_affect__the_getattr_function(self):
        catcher = self.CatchAllAttributeReads()
        self.assertMatch(__, getattr(catcher, 'any_attribute'))
    # ------------------------------------------------------------------
    class WellBehavedFooCatcher(object):
        def __getattribute__(self, attr_name):
            if attr_name[:3] == "foo":
                return "Foo to you too"
            else:
                return \
                    super(AboutAttributeAccess.WellBehavedFooCatcher, self). \
                    __getattribute__(attr_name)
    def test_foo_attributes_are_caught(self):
        catcher = self.WellBehavedFooCatcher()
        self.assertEqual(__, catcher.foo_bar)
        self.assertEqual(__, catcher.foo_baz)
    def test_non_foo_messages_are_treated_normally(self):
        catcher = self.WellBehavedFooCatcher()
        try:
            catcher.normal_undefined_attribute
        except AttributeError as ex:
            self.assertMatch(__, ex[0])
    # ------------------------------------------------------------------
    global stack_depth
    stack_depth = 0
    class RecursiveCatcher(object):
        def __init__(self):
            global stack_depth
            stack_depth = 0
            self.no_of_getattribute_calls = 0
        def __getattribute__(self, attr_name):
            #Uncomment for debugging info:
            #print 'Debug __getattribute__(' + type(self).__name__ + \
            #    "." + attr_name + ") dict=" + str(self.__dict__)
            # We need something that is outside the scope of this class:
            global stack_depth
            stack_depth += 1
            if stack_depth <= 10:  # to prevent a stack overflow
                self.no_of_getattribute_calls += 1
                # Oops! We just accessed an attribute: no_of_getattribute_calls
                # Guess what happens when self.no_of_getattribute_calls is
                # accessed?
            # Using 'object' directly because using super() here will also
            # trigger a __getattribute__() call.
            return object.__getattribute__(self, attr_name)
        def my_method(self):
            pass
    def test_getattribute_is_a_bit_overzealous_sometimes(self):
        catcher = self.RecursiveCatcher()
        catcher.my_method()
        global stack_depth
        self.assertEqual(__, stack_depth)
    # ------------------------------------------------------------------
    class MinimalCatcher(object):
        class DuffObject(object):
            pass
        def __init__(self):
            self.no_of_getattr_calls = 0
        def __getattr__(self, attr_name):
            self.no_of_getattr_calls += 1
            return self.DuffObject
        def my_method(self):
            pass
    def test_getattr_ignores_known_attributes(self):
        catcher = self.MinimalCatcher()
        catcher.my_method()
        self.assertEqual(__, catcher.no_of_getattr_calls)
    def test_getattr_only_catches_unknown_attributes(self):
        catcher = self.MinimalCatcher()
        catcher.purple_flamingos()
        catcher.free_pie()
        self.assertEqual(__,
            catcher.give_me_duff_or_give_me_death().__class__.__name__)
        self.assertEqual(__, catcher.no_of_getattr_calls)
    # ------------------------------------------------------------------
    class PossessiveSetter(object):
        def __setattr__(self, attr_name, value):
            new_attr_name = attr_name
            if attr_name[-5:] == 'comic':
                new_attr_name = "my_" + new_attr_name
            elif attr_name[-3:] == 'pie':
                new_attr_name = "a_" + new_attr_name
            object.__setattr__(self, new_attr_name, value)
    def test_setattr_intercepts_attribute_assignments(self):
        fanboy = self.PossessiveSetter()
        fanboy.comic = 'The Laminator, issue #1'
        fanboy.pie = 'blueberry'
        self.assertEqual(__, fanboy.a_pie)
        # NOTE: Change the prefix to make this next assert pass
        prefix = '__'
        self.assertEqual(
            "The Laminator, issue #1",
            getattr(fanboy, prefix + '_comic'))
    # ------------------------------------------------------------------
    class ScarySetter(object):
        def __init__(self):
            self.num_of_coconuts = 9
            self._num_of_private_coconuts = 2
        def __setattr__(self, attr_name, value):
            new_attr_name = attr_name
            if attr_name[0] != '_':
                new_attr_name = "altered_" + new_attr_name
            object.__setattr__(self, new_attr_name, value)
    def test_it_modifies_external_attribute_as_expected(self):
        setter = self.ScarySetter()
        setter.e = "mc hammer"
        self.assertEqual(__, setter.altered_e)
    def test_it_mangles_some_internal_attributes(self):
        setter = self.ScarySetter()
        try:
            coconuts = setter.num_of_coconuts
        except AttributeError:
            self.assertEqual(__, setter.altered_num_of_coconuts)
    def test_in_this_case_private_attributes_remain_unmangled(self):
        setter = self.ScarySetter()
        self.assertEqual(__, setter._num_of_private_coconuts)
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