Disabling Python 3.2 ResourceWarning

Question

Python 3.2 introduced ResourceWarning for unclosed system resources (network sockets, files):

Though the code runs clean in production, I am getting a lot of following warnings when running unit tests due to use of third party libraries where the warning occurs. I could fix the library, but on the other hand it were much simpler just to ignore it during the test run.

 block_io-python/block_io/__init__.py:182: ResourceWarning: unclosed <ssl.SSLSocket fd=11, family=AddressFamily.AF_INET, type=SocketType.SOCK_STREAM, proto=6, laddr=('x', 58395), raddr=('x, 443)>

What is the way to disable these warnings? I tried the following but no effect:

 warnings.filterwarnings("ignore", category=ResourceWarning)

(Run during unit test import time).

Answer 1

I found the culprit. You say you set your filter during import time. However, since Python 3.2 the unittest module has been updated to set the warning filter to default. See Section 29.5.5. Basically, unittest overwrites your warning filter preferences after it has finished importing your modules.

For example.

my_tests.py

import socket
import unittest
import warnings

warnings.simplefilter("ignore", ResourceWarning)

def abusesocket():
    s = socket.socket()
    s.connect(("www.google.com", 80))

class Test(unittest.TestCase):

    def test1(self):
        print("test1")
        abusesocket()
        print("module import warning filter nixed")

    def test2(self):
        print("test2")
        warnings.simplefilter("ignore", ResourceWarning)
        abusesocket()
        print("higher warning filter okay")

Gives the following output

$ python3 -m unittest  my_tests.py 
test1
/home/user/my_tests.py:15: ResourceWarning: unclosed <socket.socket fd=3, family=AddressFamily.AF_INET, type=SocketType.SOCK_STREAM, proto=0, laddr=('x.x.x.x', 52332), raddr=('31.55.166.217', 80)>
  abusesocket()
module import warning filter nixed
.test2
higher warning filter okay
.
----------------------------------------------------------------------
Ran 2 tests in 0.347s

OK

Solution

unittest appears to reset the warning filter after each test. So you'll have clear the filter at the start of each test. Probably best to use a decorator to wrap your test functions.

def ignore_warnings(test_func):
    def do_test(self, *args, **kwargs):
        with warnings.catch_warnings():
            warnings.simplefilter("ignore", ResourceWarning)
            test_func(self, *args, **kwargs)
    return do_test

class Test(unittest.TestCase):

    @ignore_warnings
    def test1(self):
        abusesocket()

Answer 2

unittest.main(warnings='ignore')

Answer 3

This alternative worked for me:

    def setUp(self):
        if not sys.warnoptions:
            import warnings
            warnings.simplefilter("ignore")

See: Standard Library docs - Overriding the default filter

Answer 4

I used this to disable only the ResourceWarning warning before a test and re-enable it afterwards.

import unittest
import warnings

class MyTestCase(unittest.TestCase):

    def setUp(self):
        warnings.simplefilter("ignore", ResourceWarning)

    def tearDown(self):
        warnings.simplefilter("default", ResourceWarning)

Also see: Different options besides "default" and "ignore"

Answer 5

Setting it once for all methods at the class level seems more efficient than repeatedly as an instance-level setUp():

    @classmethod
    def setUpClass(cls):
        warnings.simplefilter("ignore")