Restricted set operations on python dictionary key views

Question

Lets see the code snippet below:

d = {1:1}
keys = d.keys()

print(keys & {1,2,3})# {1}
d[2] = 2
print(keys & {1,2,3}) # {1,2} # keys() is a view/reference
print({1,2}.issubset({1,2,3})) # True
print(keys.issubset({1,2,3})) # 'dict_keys' object has no attribute 'issubset'

It is mentioned in the official documents on dictionary view objects:

Keys views are set-like since their entries are unique and hashable. .. Then these set operations are available (“other” refers either to another view or a set): [&,|, ^, ^]

If the keys are set-like, why are the set operation on them restricted to those four infix operations. Why, for example, side-effect free operation like issuperset or issubset not permitted?

Answer 1

Why, for example, are not side-effect free operation like issuperset or issubset operation not permitted?

They are; you just have to use the >= and <= operators:

print(keys <= {1, 2, 3})

They also support isdisjoint in method form, since there's no operator for it:

print(keys.isdisjoint({1, 2, 3}))