Python Threading example code

example-python-threads.py

import concurrent.futures
from http.client import HTTPException
import threading
import time

def output(message):
    print(f"{time.time_ns()}: {message}")

invalid_item_names = ["item4", "item6"]
fatal_item_names = ["item2"]

def validate_item(item: dict) -> list:
    output(f"validate_item(): {item["name"]}")
    time.sleep(2)
    validation_err = []
    if(item["name"] in invalid_item_names):
        message = f"{item["name"]} is invalid"
        output(message)
        validation_err.append(message)
        return validation_err
    if(item["name"] in fatal_item_names):
        message = f"{item["name"]} is fatal"
        output(message)
        raise HTTPException(message)
    output(f"{item["name"]} sleeping for {item["sleep-for"]} seconds")
    time.sleep(item["sleep-for"])
    output(f"{item["name"]} sleep complete")
    return validation_err

def validate_items(items: dict) -> list:
    error_list = []
    error_list_lock = threading.Lock()

    def validate_item_wrapper(item: str):
        validation_err = None
        try:
            validation_err = validate_item(item)
        except Exception as err:
            output(f"validate_item_wrapper exception for item: {item["name"]}")
            validation_err = ["There was an internal error, please see logs for details"]
        with error_list_lock:
            error_list.extend(validation_err)
        # error_list.extend(validation_err)

    num_workers = 3
    with concurrent.futures.ThreadPoolExecutor(max_workers=num_workers) as executor:
        for item in items:
            executor.submit(validate_item_wrapper, item)
        executor.shutdown()
    output(f"error_list: {error_list}")

items = [
    {"name": "item1", "sleep-for": 10},
    {"name": "item2", "sleep-for": 10},
    {"name": "item3", "sleep-for": 10},
    {"name": "item4", "sleep-for": 10},
    {"name": "item5", "sleep-for": 10},
    {"name": "item6", "sleep-for": 10},
    {"name": "item7", "sleep-for": 10},
]
validate_items(items)

output.log

% python3 example-python-threads.py
1740495021346587000: validate_item(): item1
1740495021346692000: validate_item(): item2
1740495021346771000: validate_item(): item3
1740495023350515000: item3 sleeping for 10 seconds
1740495023350597000: item1 sleeping for 10 seconds
1740495023350618000: item2 is fatal
1740495023350872000: validate_item_wrapper exception for item: item2
1740495023351049000: validate_item(): item4
1740495025358058000: item4 is invalid
1740495025358373000: validate_item(): item5
1740495027359090000: item5 sleeping for 10 seconds
1740495033355978000: item3 sleep complete
1740495033356063000: item1 sleep complete
1740495033356317000: validate_item(): item6
1740495033356442000: validate_item(): item7
1740495035361599000: item7 sleeping for 10 seconds
1740495035361682000: item6 is invalid
1740495037364423000: item5 sleep complete
1740495045366882000: item7 sleep complete
1740495045367448000: error_list: ['There was an internal error, please see logs for details', 'item4 is invalid', 'item6 is invalid']