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item_010.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.
### Start book environment setup
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)
### End book environment setup
print("Example 1")
a = b"h\x65llo"
print(type(a))
print(list(a))
print(a)
print("Example 2")
a = "a\u0300 propos"
print(type(a))
print(list(a))
print(a)
print("Example 3")
def to_str(bytes_or_str):
if isinstance(bytes_or_str, bytes):
value = bytes_or_str.decode("utf-8")
else:
value = bytes_or_str
return value # Instance of str
print(repr(to_str(b"foo")))
print(repr(to_str("bar")))
print("Example 4")
def to_bytes(bytes_or_str):
if isinstance(bytes_or_str, str):
value = bytes_or_str.encode("utf-8")
else:
value = bytes_or_str
return value # Instance of bytes
print(repr(to_bytes(b"foo")))
print(repr(to_bytes("bar")))
print("Example 5")
print(b"one" + b"two")
print("one" + "two")
print("Example 6")
try:
b"one" + "two"
except:
logging.exception('Expected')
else:
assert False
print("Example 7")
try:
"one" + b"two"
except:
logging.exception('Expected')
else:
assert False
print("Example 8")
assert b"red" > b"blue"
assert "red" > "blue"
print("Example 9")
try:
assert "red" > b"blue"
except:
logging.exception('Expected')
else:
assert False
print("Example 10")
try:
assert b"blue" < "red"
except:
logging.exception('Expected')
else:
assert False
print("Example 11")
print(b"foo" == "foo")
print("Example 12")
blue_bytes = b"blue"
blue_str = "blue"
print(b"red %s" % blue_bytes)
print("red %s" % blue_str)
print("Example 13")
try:
print(b"red %s" % blue_str)
except:
logging.exception('Expected')
else:
assert False
print("Example 14")
print("red %s" % blue_bytes)
print(f"red {blue_bytes}")
print("Example 15")
try:
with open("data.bin", "w") as f:
f.write(b"\xf1\xf2\xf3\xf4\xf5")
except:
logging.exception('Expected')
else:
assert False
print("Example 16")
with open("data.bin", "wb") as f:
f.write(b"\xf1\xf2\xf3\xf4\xf5")
print("Example 17")
try:
# Silently force UTF-8 here to make sure this test fails on
# all platforms. cp1252 considers these bytes valid on Windows.
real_open = open
def open(*args, **kwargs):
kwargs["encoding"] = "utf-8"
return real_open(*args, **kwargs)
with open("data.bin", "r") as f:
data = f.read()
except:
logging.exception('Expected')
else:
assert False
print("Example 18")
# Restore the overloaded open above.
open = real_open
with open("data.bin", "rb") as f:
data = f.read()
assert data == b"\xf1\xf2\xf3\xf4\xf5"
print("Example 19")
with open("data.bin", "r", encoding="cp1252") as f:
data = f.read()
assert data == "ñòóôõ"