Python namedtuple in a boolean context

Question

When a Python tuple is used in a boolean context, it is considered True if and only if it is not empty.

Does the same apply to instances of collections.namedtuple?

Answer 1

Yes, but in general you probably won't ever see it happen, since you specify names for each value in the namedtuple. Specifying no names would allow you to create an empty tuple type, but such a type would not be very useful, since its instances will always be empty:

>>> empty = collections.namedtuple("empty", [])
>>> empty()
empty()
>>> bool(empty())
False

Answer 2

Yes. You can see this by inspecting a named tuple class.

One way to do so is to view a named tuple class's source code, using ._source in Python 3.3 or later, or the verbose=True option to namedtuple(). You will see that named tuples extend tuple, and don't override the __nonzero__() or __len__() methods. This means they use the same logic as tuple, like you thought.

You can also check a named tuple class's __nonzero__ and __len__ attributes. You will see that it has no __nonzero__ attribute defined, and that the __len__ attribute is the same as the one for tuple:

>>> A = namedtuple('A', ['x'])
>>> A.__len__ == tuple.__len__
True

Answer 3

In theory, yes, but you can't create an empty instance of any useful namedtuple, because when you create a namedtuple type, you have to specify the number of elements up front. So the only way you can have an empty namedtuple is to have a namedtuple type that is always empty, in which case it serves no purpose.