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executable file
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#!/usr/bin/env PYTHONHASHSEED=1234 python3
# Copyright 2014-2024 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.
### 책 예제에 맞는 환경 설정을 시작함
import random
random.seed(1234)
import logging
from pprint import pprint
from sys import stdout as STDOUT
# 모든 출력을 임시 디렉터리로 보냄
import atexit
import gc
import io
import os
import tempfile
TEST_DIR = tempfile.TemporaryDirectory()
atexit.register(TEST_DIR.cleanup)
# 윈도우에서 프로세스가 제대로 종료되도록 함
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)
### 책 예제에 맞는 환경설정 끝
print("아이템 60")
print("Example 1")
class Homework:
def __init__(self):
self._grade = 0
@property
def grade(self):
return self._grade
@grade.setter
def grade(self, value):
if not (0 <= value <= 100):
raise ValueError("점수는 0 이상 100 이하여야 함")
self._grade = value
print("Example 2")
galileo = Homework()
galileo.grade = 95
assert galileo.grade == 95
print("Example 3")
class Exam:
def __init__(self):
self._writing_grade = 0
self._math_grade = 0
@staticmethod
def _check_grade(value):
if not (0 <= value <= 100):
raise ValueError("점수는 0 이상 100 이하여야 함")
print("Example 4")
@property
def writing_grade(self):
return self._writing_grade
@writing_grade.setter
def writing_grade(self, value):
self._check_grade(value)
self._writing_grade = value
@property
def math_grade(self):
return self._math_grade
@math_grade.setter
def math_grade(self, value):
self._check_grade(value)
self._math_grade = value
galileo = Exam()
galileo.writing_grade = 85
galileo.math_grade = 99
assert galileo.writing_grade == 85
assert galileo.math_grade == 99
print("Example 5")
class Grade:
def __get__(self, instance, instance_type):
pass
def __set__(self, instance, value):
pass
class Exam:
# Class attributes
math_grade = Grade()
writing_grade = Grade()
science_grade = Grade()
print("Example 6")
exam = Exam()
exam.writing_grade = 40
print("Example 7")
Exam.__dict__["writing_grade"].__set__(exam, 40)
print("Example 8")
exam.writing_grade
print("Example 9")
Exam.__dict__["writing_grade"].__get__(exam, Exam)
print("Example 10")
class Grade:
def __init__(self):
self._value = 0
def __get__(self, instance, instance_type):
return self._value
def __set__(self, instance, value):
if not (0 <= value <= 100):
raise ValueError("점수는 0 이상 100 이하여야 함")
self._value = value
print("Example 11")
class Exam:
math_grade = Grade()
writing_grade = Grade()
science_grade = Grade()
first_exam = Exam()
first_exam.writing_grade = 82
first_exam.science_grade = 99
print("쓰기", first_exam.writing_grade)
print("과학", first_exam.science_grade)
print("Example 12")
second_exam = Exam()
second_exam.writing_grade = 75
print(f"두번째 {second_exam.writing_grade} 는 맞음")
print(f"첫번째 {first_exam.writing_grade} 는 틀림; " f"82가 맞는 값임")
print("Example 13")
class DictGrade:
def __init__(self):
self._values = {}
def __get__(self, instance, instance_type):
if instance is None:
return self
return self._values.get(instance, 0)
def __set__(self, instance, value):
if not (0 <= value <= 100):
raise ValueError("점수는 0 이상 100 이하여야 함")
self._values[instance] = value
class DictExam:
math_grade = DictGrade()
writing_grade = DictGrade()
science_grade = DictGrade()
first_exam = DictExam()
first_exam.math_grade = 78
second_exam = DictExam()
second_exam.math_grade = 89
print(first_exam.math_grade)
print(second_exam.math_grade)
print("Example 14")
class NamedGrade:
def __set_name__(self, owner, name):
self.internal_name = "_" + name
print("Example 15")
def __get__(self, instance, instance_type):
if instance is None:
return self
return getattr(instance, self.internal_name)
def __set__(self, instance, value):
if not (0 <= value <= 100):
raise ValueError("점수는 0 이상 100 이하여야 함")
setattr(instance, self.internal_name, value)
print("Example 16")
class NamedExam:
math_grade = NamedGrade()
writing_grade = NamedGrade()
science_grade = NamedGrade()
first_exam = NamedExam()
first_exam.math_grade = 78
first_exam.writing_grade = 89
first_exam.science_grade = 94
print(first_exam.__dict__)