effectivepython/example_code/item_40.py at master · sharc007/effectivepython · GitHub

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#!/usr/bin/env PYTHONHASHSEED=1234 python3

# 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.

# Reproduce book environment

import random

random.seed(1234)

import logging

from pprint import pprint

from sys import stdout as STDOUT

# Write all output to a temporary directory

import atexit

import gc

import io

import os

import tempfile

TEST_DIR = tempfile.TemporaryDirectory()

atexit.register(TEST_DIR.cleanup)

# Make sure Windows processes exit cleanly

OLD_CWD = os.getcwd()

atexit.register(lambda: os.chdir(OLD_CWD))

os.chdir(TEST_DIR.name)

def close_open_files():

everything = gc.get_objects()

for obj in everything:

if isinstance(obj, io.IOBase):

obj.close()

atexit.register(close_open_files)

# Example 1

class MyBaseClass:

def __init__(self, value):

self.value = value

class MyChildClass(MyBaseClass):

def __init__(self):

MyBaseClass.__init__(self, 5)

def times_two(self):

return self.value * 2

foo = MyChildClass()

assert foo.times_two() == 10

# Example 2

class TimesTwo:

def __init__(self):

self.value *= 2

class PlusFive:

def __init__(self):

self.value += 5

# Example 3

class OneWay(MyBaseClass, TimesTwo, PlusFive):

def __init__(self, value):

MyBaseClass.__init__(self, value)

TimesTwo.__init__(self)

PlusFive.__init__(self)

# Example 4

foo = OneWay(5)

print('First ordering value is (5 * 2) + 5 =', foo.value)

# Example 5

class AnotherWay(MyBaseClass, PlusFive, TimesTwo):

def __init__(self, value):

MyBaseClass.__init__(self, value)

TimesTwo.__init__(self)

PlusFive.__init__(self)

# Example 6

bar = AnotherWay(5)

print('Second ordering value is', bar.value)

# Example 7

class TimesSeven(MyBaseClass):

def __init__(self, value):

MyBaseClass.__init__(self, value)

self.value *= 7

class PlusNine(MyBaseClass):

def __init__(self, value):

MyBaseClass.__init__(self, value)

self.value += 9

# Example 8

class ThisWay(TimesSeven, PlusNine):

def __init__(self, value):

TimesSeven.__init__(self, value)

PlusNine.__init__(self, value)

foo = ThisWay(5)

print('Should be (5 * 7) + 9 = 44 but is', foo.value)

# Example 9

class MyBaseClass:

def __init__(self, value):

self.value = value

class TimesSevenCorrect(MyBaseClass):

def __init__(self, value):

super().__init__(value)

self.value *= 7

class PlusNineCorrect(MyBaseClass):

def __init__(self, value):

super().__init__(value)

self.value += 9

# Example 10

class GoodWay(TimesSevenCorrect, PlusNineCorrect):

def __init__(self, value):

super().__init__(value)

foo = GoodWay(5)

print('Should be 7 * (5 + 9) = 98 and is', foo.value)

# Example 11

mro_str = '\n'.join(repr(cls) for cls in GoodWay.mro())

print(mro_str)

# Example 12

class ExplicitTrisect(MyBaseClass):

def __init__(self, value):

super(ExplicitTrisect, self).__init__(value)

self.value /= 3

assert ExplicitTrisect(9).value == 3

# Example 13

class AutomaticTrisect(MyBaseClass):

def __init__(self, value):

super(__class__, self).__init__(value)

self.value /= 3

class ImplicitTrisect(MyBaseClass):

def __init__(self, value):

super().__init__(value)

self.value /= 3

assert ExplicitTrisect(9).value == 3

assert AutomaticTrisect(9).value == 3

assert ImplicitTrisect(9).value == 3

effectivepython/example_code/item_40.py at master · sharc007/effectivepython · GitHub

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