import time
import threading
def echo(k):
    time.sleep(k)
    for i in range(k):
        print('поток', k, 'шаг', i)
key = [5, 1, 3]
for k in key:
    threading.Thread(target=echo, args=(k,)).start()

import gevent
import time
def echo(k):
    time.sleep(k)
    for i in range(k):
        print('поток', k, 'шаг', i)
key = [5, 1, 3]
  
jobs = [gevent.spawn(echo, k) for k in key]
gevent.joinall(jobs)

import gevent
import time
from gevent.threadpool import ThreadPool
def echo(k):
    time.sleep(k)
    for i in range(k):
        print('поток', k, 'шаг', i)
key = [5, 1, 3]
pool = ThreadPool(5)
jobs = [pool.spawn(echo, k) for k in key]
gevent.joinall(jobs)