python pools example

python_pools.py

# https://www.geeksforgeeks.org/python-map-function/

import time

def foo(bar):
  time.sleep(2)
  return 'foo ' + str(bar)

from multiprocessing.pool import ThreadPool
pool = ThreadPool(processes=4)

async_results = []

for i in range(4):
  async_result = pool.apply_async(foo, (i,)) # tuple of args for foo
  async_results.append(async_result)

# do some other stuff in the main process

pool.close()
pool.join()

print('other stuff')

# for async_result in async_results:
#   print(async_result.get())

res = list(map(lambda asyncRes: asyncRes.get(), async_results))
print(res)

print(list(map((lambda x: x + 1), [1,2,3])))






# from multiprocessing import Pool

# foo = {1: []}

# def f(x):
#   time.sleep(1)
#   return x

# def main():
#   pool = Pool()
#   foo[1] = pool.map(f, range(10))
#   pool.close()
#   pool.join()
#   print('sapee')
#   print (foo)

# if __name__ == '__main__':
#   main()



# # Python program to illustrate  
# # the concept of race condition 
# # in multiprocessing 
# import multiprocessing 
  
# # function to withdraw from account 
# def withdraw(balance):     
#     for _ in range(10): 
#         balance.value = balance.value - 1
  
# # function to deposit to account 
# def deposit(balance):     
#     for _ in range(10): 
#         balance.value = balance.value + 1
  


# # initial balance (in shared memory) 
# balance = multiprocessing.Value('i', 100) 

# # creating new processes 
# p1 = multiprocessing.Process(target=withdraw, args=(balance,)) 
# p2 = multiprocessing.Process(target=deposit, args=(balance,)) 

# # starting processes 
# p1.start() 
# p2.start() 

# # wait until processes are finished 
# p1.join() 
# p2.join() 

# # print final balance 
# print("Final balance = {}".format(balance.value))