Tuples inside a list

Question

There is a challenge question with code:

my_list = [([]), [()]]
for i in my_list:
print(bool(i), sep=' ')

Can anybody explain why is the output 'False True'?

Answer 1

Your outer list has two comma-separated elements, ([]) and [()].

The first set of parentheses just disappears, because you can't write a tuple like that.

The syntax for a single-element tuple would be: ([],)

The syntax for an *empty* tuple on the other hand is ().

So parentheses with 0 or 2+ elements are tuples, while parentheses with 1 element just work for grouping unless you add a comma.

Answer 2

HonFu thank you very much, now it is clearer for me.

Answer 3

I know about empty-False, but why as of the first item () is expression grouping and as of the second expression it is an empty tuple when the both ()'s are inside a list?

Answer 4

Sergei Romanov
() this is considers as empty as nothing is present inside the parenthesis. but when it's inside any list then it considered as an list elements.

[] this is considered as an empty list without tuple.

([]) this whole statement is considered as empty so bool i when refere to index 0 elements it return false as it reading empty thing which is give false by bool.

The parentheses in ([]) just reorders the expression which in the end is just the same thing as []

[()] is an empty tuple in a list
When converting any container to a bool, an empty container is False, otherwise it is True
my_list is[ [], [()] ] so the for loop iterates twice

bool( [] ) == False
bool( [()] ) == True (because the list is not actually empty; it contains an empty tuple)