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item_023.py
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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 23")
print("Example 1")
import random
def flip_coin():
if random.randint(0, 1) == 0:
return "앞"
else:
return "뒤"
def flip_is_heads():
return flip_coin() == "앞"
print("Example 2")
flips = [flip_is_heads() for _ in range(20)]
all_heads = False not in flips
assert not all_heads # True일 확률이 매우 낮음
print("Example 3")
all_heads = True
for _ in range(100):
if not flip_is_heads():
all_heads = False
break
assert not all_heads # True일 확률이 매우 낮음
print("Example 4")
print("모두 참일 때:")
print(all([1, 2, 3]))
print(1 and 2 and 3)
print("하나라도 거짓일 때:")
print(all([1, 0, 3]))
print(1 and 0 and 3)
print("Example 5")
all_heads = all(flip_is_heads() for _ in range(20))
assert not all_heads
print("Example 6")
all_heads = all([flip_is_heads() for _ in range(20)]) # 잘못됨
assert not all_heads
print("Example 7")
def repeated_is_heads(count):
for _ in range(count):
yield flip_is_heads() # 제너레이터
all_heads = all(repeated_is_heads(20))
assert not all_heads
print("Example 8")
def flip_is_tails():
return flip_coin() == "뒤"
print("Example 9")
print("모두 거짓일 때:")
print(any([0, False, None]))
print(0 or False or None)
print("하나라도 참일 때:")
print(any([None, 3, 0]))
print(None or 3 or 0)
print("Example 10")
all_heads = not any(flip_is_tails() for _ in range(20))
assert not all_heads
print("Example 11")
def repeated_is_tails(count):
for _ in range(count):
yield flip_is_tails()
all_heads = not any(repeated_is_tails(20))
assert not all_heads
print("Example 12")
for a in (True, False):
for b in (True, False):
assert any([a, b]) == (not all([not a, not b]))
assert all([a, b]) == (not any([not a, not b]))