133 lines
3.5 KiB
Python
Executable File
133 lines
3.5 KiB
Python
Executable File
# -*- coding: utf-8 -*-
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"""
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tests.py
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----------------------------------
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Tests for `cached-property` module.
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"""
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from time import sleep
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from threading import Lock, Thread
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import unittest
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from cached_property import cached_property
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class TestCachedProperty(unittest.TestCase):
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def test_cached_property(self):
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class Check(object):
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def __init__(self):
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self.total1 = 0
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self.total2 = 0
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@property
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def add_control(self):
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self.total1 += 1
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return self.total1
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@cached_property
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def add_cached(self):
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self.total2 += 1
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return self.total2
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c = Check()
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# The control shows that we can continue to add 1.
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self.assertEqual(c.add_control, 1)
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self.assertEqual(c.add_control, 2)
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# The cached version demonstrates how nothing new is added
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self.assertEqual(c.add_cached, 1)
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self.assertEqual(c.add_cached, 1)
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# It's customary for descriptors to return themselves if accessed
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# though the class, rather than through an instance.
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self.assertTrue(isinstance(Check.add_cached, cached_property))
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def test_reset_cached_property(self):
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class Check(object):
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def __init__(self):
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self.total = 0
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@cached_property
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def add_cached(self):
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self.total += 1
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return self.total
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c = Check()
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# Run standard cache assertion
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self.assertEqual(c.add_cached, 1)
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self.assertEqual(c.add_cached, 1)
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# Reset the cache.
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del c.add_cached
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self.assertEqual(c.add_cached, 2)
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self.assertEqual(c.add_cached, 2)
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def test_none_cached_property(self):
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class Check(object):
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def __init__(self):
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self.total = None
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@cached_property
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def add_cached(self):
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return self.total
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c = Check()
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# Run standard cache assertion
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self.assertEqual(c.add_cached, None)
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class TestThreadingIssues(unittest.TestCase):
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def test_threads(self):
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""" How well does the standard cached_property implementation work with threads?
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Short answer: It doesn't! Use threaded_cached_property instead!
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"""
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class Check(object):
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def __init__(self):
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self.total = 0
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self.lock = Lock()
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@cached_property
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def add_cached(self):
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sleep(1)
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# Need to guard this since += isn't atomic.
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with self.lock:
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self.total += 1
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return self.total
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c = Check()
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threads = []
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num_threads = 10
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for x in range(num_threads):
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thread = Thread(target=lambda: c.add_cached)
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thread.start()
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threads.append(thread)
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for thread in threads:
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thread.join()
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# Threads means that caching is bypassed.
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self.assertNotEqual(c.add_cached, 1)
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# This assertion hinges on the fact the system executing the test can
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# spawn and start running num_threads threads within the sleep period
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# (defined in the Check class as 1 second). If num_threads were to be
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# massively increased (try 10000), the actual value returned would be
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# between 1 and num_threads, depending on thread scheduling and
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# preemption.
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self.assertEqual(c.add_cached, num_threads)
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