Python: "int not callable" with multiprocessing with pool

Question

I had an error with some multiprocessing with the pool (pop index out of range) and when I tried to simplify my code to post it here I get another error, so it's kind puzzling, see the code here:

def some_function(a, b):
    return a*b

neigbhourhood = [[object() for _ in range(3)] for _ in range(3)]
result = [[object() for _ in range(3)] for _ in range(3)]
pool = Pool()
for i in range(0, 3):
    for j in range(0, 3):
        neigbhourhood[i][j] = pool.apply_async(some_function(i, j))

for k in range(0, 3):
    for l in range(0, 3):
        result[k][l] = neigbhourhood[k][l].get()
pool.close()

The traceback is about an int object not callable at the line 34 (the line with the get).

Edit: Ok it was just a typing error in the parameters of the pool.apply_async, now it's working but my real code is still randomly crashing and I can not repeat the error when I'm simplifying the code, I don't get it.

It seems that the problem is not arising from "the line with the get", but instead your passing the function result to pool.apply_async. some_function(i, j) already computes the result, what you want to do is pass the function as first parameter and the function arguments as tuple, i.e. pool.apply_async(some_function, (i, j)). — a_guest
– a_guest, Commented Jan 4, 2017 at 11:01

mic4ael · Accepted Answer · 2017-01-04 10:55:38Z

3

The problem lies in the way you are calling apply_async. It requires you to pass a function callback and arguments that will be passed to the provided function.

pool.apply.async(some_function, [x, y])

edited Jan 4, 2017 at 10:55

answered Jan 4, 2017 at 10:53

mic4ael

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2 Comments

Raphael Todo Over a year ago

Doesn't it return an ApplyResult Object (that I transform in int with the get() ) ? What should I do?

user5653854 Over a year ago

@RaphaelTodo some_function produces a result before apply_async gets called. So you will actually supply an int as callback function which obviously doesn't work

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