threading_local.py

threading_local.py

from concurrent.futures import ThreadPoolExecutor
from threading import local, get_ident

ctx = local()
ctx.counter = 0


def inc(_):
    try:
        ctx.counter += 1
    except AttributeError:
        ctx.counter = 0

    print(get_ident(), ctx.counter)


with ThreadPoolExecutor(max_workers=3) as executor:
    list(executor.map(inc, list(range(100))))


print('MainThread:', ctx.counter)