Why is there no explicit emptyness check (for example `is Empty`) in Python

Question

The Zen of Python says "Explicit is better than implicit". Yet the "pythonic" way to check for emptiness is using implicit booleaness:

if not some_sequence:     some_sequence.fill_sequence() 

This will be true if some_sequence is an empty sequence, but also if it is None or 0.

Compare with a theoretical explicit emptiness check:

if some_sequence is Empty:     some_sequence.fill_sequence() 

With some unfavorably chosen variable name the implicit booleaness to check for emptiness gets even more confusing:

if saved:     mess_up() 

Compare with:

if saved is not Empty:     mess_up() 

See also: "Python: What is the best way to check if a list is empty?". I find it ironic that the most voted answer claims that implicit is pythonic.

So is there a higher reason why there is no explicit emptiness check, like for example is Empty in Python?

Answer 1

Polymorphism in if foo: and if not foo: isn't a violation of "implicit vs explicit": it explicitly delegates to the object being checked the task of knowing whether it's true or false. What that means (and how best to check it) obviously does and must depend on the object's type, so the style guide mandates the delegation -- having application-level code arrogantly asserts it knows better than the object would be the height of folly.

Moreover, X is Whatever always, invariably means that X is exactly the same object as Whatever. Making a totally unique exception for Empty or any other specific value of Whatever would be absurd -- hard to imagine a more unPythonic approach. And "being exactly the same object" is obviously transitive -- so you could never any more have distinct empty lists, empty sets, empty dicts... congratulations, you've just designed a completely unusable and useless language, where every empty container crazily "collapses" to a single empty container object (just imagine the fun when somebody tries to mutate an empty container...?!).