#!/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