Expert Python Programming - Third Edition

Using two-way queues

The other issue that we are now able to solve is the potentially problematic printing of the output in threads. It would be much better to leave such a responsibility to the main thread that started the worker threads. We can handle that by providing another queue that will be responsible for collecting results from our workers. Here is the complete code that puts everything together, with the main changes highlighted:

import timefrom queue import Queue, Emptyfrom threading import Threadimport requestsSYMBOLS = ('USD', 'EUR', 'PLN', 'NOK', 'CZK')BASES = ('USD', 'EUR', 'PLN', 'NOK', 'CZK')THREAD_POOL_SIZE = 4def fetch_rates(base):    response = requests.get(        f"https://api.exchangeratesapi.io/latest?base={base}"    ) response.raise_for_status() ...