#!/usr/bin/env python3 # Copyright 2014 Brett Slatkin, Pearson Education Inc. # # Licensed under the Apache License, Version 2.0 (the "License"); # you may not use this file except in compliance with the License. # You may obtain a copy of the License at # # http://www.apache.org/licenses/LICENSE-2.0 # # Unless required by applicable law or agreed to in writing, software # distributed under the License is distributed on an "AS IS" BASIS, # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. # See the License for the specific language governing permissions and # limitations under the License. # Preamble to mimick book environment import logging from pprint import pprint from sys import stdout as STDOUT # Example 1 class MyObject(object): def __init__(self): self.public_field = 5 self.__private_field = 10 def get_private_field(self): return self.__private_field # Example 2 foo = MyObject() assert foo.public_field == 5 # Example 3 assert foo.get_private_field() == 10 # Example 4 try: foo.__private_field except: logging.exception('Expected') else: assert False # Example 5 class MyOtherObject(object): def __init__(self): self.__private_field = 71 @classmethod def get_private_field_of_instance(cls, instance): return instance.__private_field bar = MyOtherObject() assert MyOtherObject.get_private_field_of_instance(bar) == 71 # Example 6 try: class MyParentObject(object): def __init__(self): self.__private_field = 71 class MyChildObject(MyParentObject): def get_private_field(self): return self.__private_field baz = MyChildObject() baz.get_private_field() except: logging.exception('Expected') else: assert False # Example 7 assert baz._MyParentObject__private_field == 71 # Example 8 print(baz.__dict__) # Example 9 class MyClass(object): def __init__(self, value): self.__value = value def get_value(self): return str(self.__value) foo = MyClass(5) assert foo.get_value() == '5' # Example 10 class MyIntegerSubclass(MyClass): def get_value(self): return int(self._MyClass__value) foo = MyIntegerSubclass(5) assert foo.get_value() == 5 # Example 11 class MyBaseClass(object): def __init__(self, value): self.__value = value def get_value(self): return self.__value class MyClass(MyBaseClass): def get_value(self): return str(super().get_value()) class MyIntegerSubclass(MyClass): def get_value(self): return int(self._MyClass__value) # Example 12 try: foo = MyIntegerSubclass(5) foo.get_value() except: logging.exception('Expected') else: assert False # Example 13 class MyClass(object): def __init__(self, value): # This stores the user-supplied value for the object. # It should be coercible to a string. Once assigned for # the object it should be treated as immutable. self._value = value def get_value(self): return str(self._value) class MyIntegerSubclass(MyClass): def get_value(self): return self._value foo = MyIntegerSubclass(5) assert foo.get_value() == 5 # Example 14 class ApiClass(object): def __init__(self): self._value = 5 def get(self): return self._value class Child(ApiClass): def __init__(self): super().__init__() self._value = 'hello' # Conflicts a = Child() print(a.get(), 'and', a._value, 'should be different') # Example 15 class ApiClass(object): def __init__(self): self.__value = 5 def get(self): return self.__value class Child(ApiClass): def __init__(self): super().__init__() self._value = 'hello' # OK! a = Child() print(a.get(), 'and', a._value, 'are different')