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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
a = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
squares = []
for x in a:
squares.append(x**2)
print(squares)
# Example 2
squares = [x**2 for x in a] # List comprehension
print(squares)
# Example 3
alt = map(lambda x: x ** 2, a)
assert list(alt) == squares, f'{alt} {squares}'
# Example 4
even_squares = [x**2 for x in a if x % 2 == 0]
print(even_squares)
# Example 5
alt = map(lambda x: x**2, filter(lambda x: x % 2 == 0, a))
assert even_squares == list(alt)
# Example 6
even_squares_dict = {x: x**2 for x in a if x % 2 == 0}
threes_cubed_set = {x**3 for x in a if x % 3 == 0}
print(even_squares_dict)
print(threes_cubed_set)
# Example 7
alt_dict = dict(map(lambda x: (x, x**2),
filter(lambda x: x % 2 == 0, a)))
alt_set = set(map(lambda x: x**3,
filter(lambda x: x % 3 == 0, a)))
assert even_squares_dict == alt_dict
assert threes_cubed_set == alt_set