How can I log something with python logger only when an assert fails?

Question

@pytest.mark.usefixtures("oneTimeSetUp","setUp")
class BeyondTest(unittest.TestCase):
    log = cl.testLogger(logging.INFO)
    @pytest.fixture(autouse=True)
    def classSetup(self,oneTimeSetUp):
        self.ts = TestStatus(self.driver)
        self.bmf = BMF(self.driver)


    @pytest.mark.run(order=1)
    def test_site_to_csv(self):
        self.bmf.imagelist()
        first_column =[l[4] for l in self.bmf.csvreader]
        list_site_to_csv = [item for item in self.bmf.full_list if item not in first_column]
        self.log.INFO(list_site_to_csv)
        assert len(list_site_to_csv)<=0

So I have a csv with some data that needs to be verified on a site, I first capture data on the site append to a list "self.bmf.full_list", the csv columns are saved in the first_column list, I then compare both list and save the ones missing from csv but are present on site to the list "list_site_to_csv. The assertion is the len(list_site_to_csv)<=0. What I am trying to figure out is how to log.INFO only when an assertion fails? something like

if assert len(list_site_to_csv)<=0:
    then self.log.INFO(list_site_to_csv)

anyother suggestion on better way to handle this than a list would also be great

And you don't just want an if-statement? You could put the assertion in a try/except block to catch the exception, log, then raise the exception. — Arya McCarthy
– Arya McCarthy, Commented Mar 31, 2020 at 2:55

slackmart · Accepted Answer · 2020-03-31 16:06:10Z

2

assert accepts a second argument. Example:

>>> list_site_to_csv = ['apples']
>>> assert not list_site_to_csv, f'It failed. List is not empty. {list_site_to_csv}'
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
AssertionError: It failed. List is not empty. ['apples']

In this case if the list_site_to_csv is not empty, the assert will pops out, and it'll show the message.

Note:

len(list_site_to_csv) <= 0 is not pythonic. For testing falsy values it's preferred to use if not my_var:.

edited Mar 31, 2020 at 16:06

answered Mar 31, 2020 at 2:54

slackmart

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