assertAlmostEqual giving TypeError: 'str' object cannot be interpreted as an integer, despite isinstance check - pytest

Question

I have some test code:
def assertSamplesEqual(self, a, b, msg=None):
if isinstance(a.value, float) and isinstance(b.value, float):
self.assertAlmostEqual(
a.value, b.value, msg or
'Samples %s and %s have different values' % (a, b))
else:
self.assertEqual(
a.value, b.value, msg or
'Samples %s and %s have different values' % (a, b))
I just swapped to assertAlmostEqual to better handle floats (I could get float or string values here, hence the isinstance conditional) and started getting the following error:
third_party/py/perfkitbenchmarker/test_util.py:52 in assertSamplesEqualUpToTimestamp
self.assertAlmostEqual(
<embedded stdlib>/unittest/case.py:882 in assertAlmostEqual
if round(diff, places) == 0:
TypeError: 'str' object cannot be interpreted as an integer
How can I be getting this string error from assertAlmostEqual, when I've just checked via isinstance that the values are floats?
I tried print(type(a.value)) & got the expected <class 'float'> response.

Answer 1

It was not a.value which was of type string, but rather the following parameter msg. Look at the function definition for assertAlmostEqual:
assertAlmostEqual(first, second, places=7, msg=None, delta=None) Note that the third parameter is places & the fourth parameter is msg. Since msg was my third parameter, it was being treated as places & resulted in the TypeError at the line if round(diff, places) == 0:.
My fix was pretty simple - add the parameter name msg=. So my new line is:
self.assertAlmostEqual(
a.value, b.value, msg=msg or
'Samples %s and %s have different values' % (a, b))
Tricky red herring - I doubted isinstance when I should have checked assertAlmostEqual!