#!/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. # Example 9 # Check types in this file with: python -m mypy from datetime import datetime from time import sleep from typing import Optional def log_typed(message: str, when: Optional[datetime]=None) -> None: """Log a message with a timestamp. Args: message: Message to print. when: datetime of when the message occurred. Defaults to the present time. """ if when is None: when = datetime.now() print(f'{when}: {message}') log_typed('Hi there!') sleep(0.1) log_typed('Hello again!')