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mutate_instance.py

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# test concurrent mutating access to a shared user instance

#

# MIT license; Copyright (c) 2016 Damien P. George on behalf of Pycom Ltd

import _thread

# the shared user class and instance

class User:

def __init__(self):

self.a = 'A'

self.b = 'B'

self.c = 'C'

user = User()

# main thread function

def th(n, lo, hi):

for repeat in range(n):

for i in range(lo, hi):

setattr(user, 'attr_%u' % i, repeat + i)

assert getattr(user, 'attr_%u' % i) == repeat + i

with lock:

global n_finished

n_finished += 1

lock = _thread.allocate_lock()

n_repeat = 30

n_range = 50 # 300 for stressful test (uses more heap)

n_thread = 4

n_finished = 0

# spawn threads

for i in range(n_thread):

_thread.start_new_thread(th, (n_repeat, i * n_range, (i + 1) * n_range))

# busy wait for threads to finish

while n_finished < n_thread:

pass

# check user instance has correct contents

print(user.a, user.b, user.c)

for i in range(n_thread * n_range):

assert getattr(user, 'attr_%u' % i) == n_repeat - 1 + i