TypeError: __str__ returned non-string (type bytes)

[Mike Dewhirst]

This is driving me insane so any hints will be greatly appreciated ...

Thanks

Mike

Here is the entire unedited test sequence plus failing code ...

Python: 3.4
Django: 1.6.9
SQLite3: memory

Creating test database for alias 'default'...
.E.E...
======================================================================
ERROR: test_checkreference_exp
(substance.tests.test_substance.TestSubstance)
----------------------------------------------------------------------
Traceback (most recent call last):
File
"C:\Users\mike\env\xxdx3\ssds\substance\tests\test_substance.py", line
57, in test_checkreference_exp
self.assertEqual(subst.checkreference('1'), True)
File "C:\Users\mike\env\xxdx3\ssds\substance\models\substance.py",
line 449, in checkreference
if checkit(self, ref):
File "C:\Users\mike\env\xxdx3\ssds\substance\models\substance.py",
line 441, in checkit
val = u"{0}".format(obj.__dict__[field])
TypeError: __str__ returned non-string (type bytes)

======================================================================
ERROR: testcheckreference_gas (substance.tests.test_substance.TestSubstance)
----------------------------------------------------------------------
Traceback (most recent call last):
File
"C:\Users\mike\env\xxdx3\ssds\substance\tests\test_substance.py", line
75, in test_checkreference_gas
self.assertEqual(subst.checkreference('1'.encode('utf-8')), True)
File "C:\Users\mike\env\xxdx3\ssds\substance\models\substance.py",
line 449, in checkreference
if checkit(self, ref):
File "C:\Users\mike\env\xxdx3\ssds\substance\models\substance.py",
line 441, in checkit
val = u"{0}".format(obj.__dict__[field])
TypeError: __str__ returned non-string (type bytes)

----------------------------------------------------------------------
Ran 7 tests in 1.281s

FAILED (errors=2)
Destroying test database for alias 'default'...

So here is the method in the substance model. The idea is that we check
to see if the user included a bracketed reference in any field of
substance or any field of a related object. I'll chop out the middle of
the method to save space.

def checkreference(self, ref):
"""Check all potential char fields for ref in square brackets
eg [1]

Give up as soon as it is found. Otherwise raise validation error.
"""
def checkit(obj, ref):
"""Return True immediately but don't return False unless all
fields have been checked."""
for field in obj.__dict__:
val = u"{0}".format(obj.__dict__[field])
if ref in val:
return True

assert(ref)
ref = "[{0}]".format(ref)
# first check self - the substance itself
if checkit(self, ref):
return True
# now each of the 1:1 and 1:n objects
try:
obj = Solid.objects.get(substance=self)
if checkit(obj, ref):
return True
except Solid.DoesNotExist:
pass
<snip lots of similar try/except blocks>
raise ValidationError("Reference {0} does not appear in any "
"field".format(ref))

... and here is one of the tests (line 57 in the traceback) in error ...

def test_checkreference_exp(self):
subst = Substance.objects.get(name="Hazsub")
exp, c = Explosive.objects.get_or_create(substance=subst)
exp.compatibility = '[1]'
exp.save()
self.assertEqual(subst.checkreference('1'), True)

[James Schneider]

What happens when you throw in a print(obj.__dict__[field]) before the val assignment? You should see on the console what value each iteration of the loop is using and see if you have a strange attribute that is throwing things out of kilter.

-James

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[Erik Cederstrand]

> Den 25/02/2015 kl. 05.33 skrev Mike Dewhirst <mi...@dewhirst.com.au>:
>
> ======================================================================
> ERROR: test_checkreference_exp (substance.tests.test_substance.TestSubstance)
> ----------------------------------------------------------------------
> Traceback (most recent call last):
> File "C:\Users\mike\env\xxdx3\ssds\substance\tests\test_substance.py", line 57, in test_checkreference_exp
> self.assertEqual(subst.checkreference('1'), True)
> File "C:\Users\mike\env\xxdx3\ssds\substance\models\substance.py", line 449, in checkreference
> if checkit(self, ref):
> File "C:\Users\mike\env\xxdx3\ssds\substance\models\substance.py", line 441, in checkit
> val = u"{0}".format(obj.__dict__[field])
> TypeError: __str__ returned non-string (type bytes)

"obj.__dict__[field]" returns an object that has a __str__ method (format() calls the __str__ method of the object to convert it to a string). The __str__ method should only return unicode data but is returning byte strings. What does "obj.__dict__[field]" return, and can you show us the __str__ method of that class?

Erik

[Mike Dewhirst]

Erik and James

I really appreciate your feedback. The problem is resolved. It was related to py3 development and py2 in production. Erik had hit the nail on the head which I discovered when I went looking at why other tests were passing and those two were not. I had been inconsistent in implementing @python_2_unicode_compatible

Thank you again

Mike