Why in Python does “0, 0 == (0, 0)” equal “(0, False)”?

Question

In Python (I checked only with Python 3.6 but I believe it should hold for many of the previous versions as well):

(0, 0) == 0, 0   # results in a two elemen         


        

Answer 1

I had a similar question. I am not a computer scientist, I am either a software engineer or a computer programmer. So I asked the python interpreter and this is what I found, empirically.

>>> t1 = ()
>>> "True" if t1 else "False"
'False'
>>> t1 = (False)     # That's because t1 is not a tuple!
>>> "True" if t1 else "False"
'False'
>>> t1 = (False,)     # t1 is a tuple.  So , is an operator as mentioned above
>>> "True" if t1 else "False"
'True'
>>> t1 = (False, 1)
>>> "True" if t1 else "False"
'True'
>>> t1 = (False, False)
>>> "True" if t1 else "False"
'True'
>>> type(False,)
<class 'bool'>
>>> type((False,))
<class 'tuple'>
>>> type(False)
<class 'bool'>
>>> type((False))
<class 'bool'>
>>>

I did a lot of testing and the only tuple I found that evaluate to False is the empty tuple.

I also learned something in this exercise. A lot of rookies use the idiom:

if BOOLEAN_EXPRESSION == False:

instead of

if not BOOLEAN_EXPRESSION:

"Why is this a bad thing to do?", they ask me. Now, I have a good answer:

>>> (False,) == False
False
>>> t1=(False,)
>>> "True" if t1 else "False"
'True'
>>> t1 == False
False
>>>
>>> t1=(False,)
>>> "True" if t1 else "False"
'True'
>>> t1 == False
False
>>> t1 is False
False
>>> not t1 is False
True
>>> not ( t1 is False )
True
>>>
>>> "True" if t1 else "False"
'True'
>>> "True" if not t1 else "False"
'False'
>>> "True" if t1 == True else "False"
'False'
>>>

So even though (False,) evaluates to False, it is not False.

I would like to thank you for asking this question to my attention. It's a great question.