Question

I have the following code condition

 if len(content_tags) >= 1 or tags_irrelevant == 'yes'\
   and lengthproblem == 0\
   and guess_language.guessLanguage(testlanguage) == 'en'\
   and len(sentences) >= 3:

The problem is about the logic and the syntax. I want this to be evaluated as false no matter if if len(sentences) is not >= 3. But this is not happening. I think I might need some parenthesis somewhere or something. HELP!

Answer 1

and has a higher precidence than or, so the ands are evaluated first, then the or, meaning that the logic you have described in text is not the logic you have described in code.

If you want the first or to be treated as a single case, then use brackets around it.

if (len(content_tags) >= 1 or tags_irrelevant == 'yes')\
   and lengthproblem == 0\
   and guess_language.guessLanguage(testlanguage) == 'en'\
   and len(sentences) >= 3:

That said, you haven’t given us a detailed explanation of the logical behaviour you want from this, so I’d suggest sitting down and working that out properly.

If you need to test your logic, then use a simple test function that prints out so you know what gets evaluated and when.

>>> def test(bool):
...    print(bool)
...    return bool
... 
>>> if test(1) or test(2) and test(3) and test(4) and test(False):
...    print("Success")
... 
1
Success
>>> if (test(1) or test(2)) and test(3) and test(4) and test(False):
...     print("Success")
... 
1
3
4
False

You can clearly see the first thing evaluated is the first and, then it tries to evaluate the left hand side of the and and so gets the or. It tries to evaluate this, gets True for the first value, and so short-circuits, returning True to the and, which also short circuits, returning True (well, actually 1, but True for the purposes of this example). When the brackets are there, it is evaluated in the way you wanted.