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

# Copyright 2014-2019 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.

# 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

def log(message, values):

if not values:

print(message)

else:

values_str = ', '.join(str(x) for x in values)

print(f'{message}: {values_str}')

log('My numbers are', [1, 2])

log('Hi there', [])

# Example 2

def log(message, *values): # The only difference

if not values:

print(message)

else:

values_str = ', '.join(str(x) for x in values)

print(f'{message}: {values_str}')

log('My numbers are', 1, 2)

log('Hi there') # Much better

# Example 3

favorites = [7, 33, 99]

log('Favorite colors', *favorites)

# Example 4

def my_generator():

for i in range(10):

yield i

def my_func(*args):

print(args)

it = my_generator()

my_func(*it)

# Example 5

def log(sequence, message, *values):

if not values:

print(f'{sequence} - {message}')

else:

values_str = ', '.join(str(x) for x in values)

print(f'{sequence} - {message}: {values_str}')

log(1, 'Favorites', 7, 33) # New with *args OK

log(1, 'Hi there') # New message only OK

log('Favorite numbers', 7, 33) # Old usage breaks