0Concurrent means, more than one task happening at a time in interleaved fashion, (ie.,)Task 'A' starts, and Task 'B' starts before task 'A' finish, after processing its(A and B) own purpose both the task will finish, you can assume, only one statement will execute in any time.
Here we should not confuse concurrent with parallel:
Parallel, is running more than one task in different process at a time, you can assume, it will execute as many statements as much thread you have assigned/created.
Concurrent vs Parallel Execution:
#Concurrent(Allows to deal with I/O while computing)print('------- Concurrent Programming in Python --------')import asyncio
#This library will work only from python3.5@asyncio.coroutinedef countdown(number, n): while n > 0: print('T-minus', n, '({})'.format(number)) yield from asyncio.sleep(1) n -= 1loop = asyncio.get_event_loop()tasks = [ asyncio.ensure_future(countdown("A", 5)), asyncio.ensure_future(countdown("B", 5)), asyncio.ensure_future(countdown("c", 5))]loop.run_until_complete(asyncio.wait(tasks))loop.close()
#Parallel(helps to increase the throughput of the machine)print('------- Parallel Programming in Python --------')from multiprocessing.dummy import Pool as ThreadPool
#Above library will work only from python3.5import timedef squareNumber(nn): time.sleep(5) for i in range(nn): print (i)pool = ThreadPool(2) #by increasing the thread count(2),it will create a new thread to handle parallel executionresult=pool.map(squareNumber, [2,4,6])pool.close()pool.join() 
