#!/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 from threading import Lock lock = Lock() with lock: # Do something while maintaining an invariant pass # Example 2 lock.acquire() try: # Do something while maintaining an invariant pass finally: lock.release() # Example 3 import logging logging.getLogger().setLevel(logging.WARNING) def my_function(): logging.debug('Some debug data') logging.error('Error log here') logging.debug('More debug data') # Example 4 my_function() # Example 5 from contextlib import contextmanager @contextmanager def debug_logging(level): logger = logging.getLogger() old_level = logger.getEffectiveLevel() logger.setLevel(level) try: yield finally: logger.setLevel(old_level) # Example 6 with debug_logging(logging.DEBUG): print('* Inside:') my_function() print('* After:') my_function() # Example 7 with open('my_output.txt', 'w') as handle: handle.write('This is some data!') # Example 8 @contextmanager def log_level(level, name): logger = logging.getLogger(name) old_level = logger.getEffectiveLevel() logger.setLevel(level) try: yield logger finally: logger.setLevel(old_level) # Example 9 with log_level(logging.DEBUG, 'my-log') as logger: logger.debug(f'This is a message for {logger.name}!') logging.debug('This will not print') # Example 10 logger = logging.getLogger('my-log') logger.debug('Debug will not print') logger.error('Error will print') # Example 11 with log_level(logging.DEBUG, 'other-log') as logger: logger.debug(f'This is a message for {logger.name}!') logging.debug('This will not print')