im curious about how the logical operators work in sets. cosider this:
x = set('abcde')
y = set('bdxyz')
# union
print(x | y) # output: {'d', 'b', 'y', 'e', 'z', 'x', 'c', 'a'}
print(x or y) # output: {'d', 'b', 'e', 'c', 'a'}
# intersection
print(x and y) # output: {'d', 'b', 'y', 'z', 'x'}
print(x & y) # output: {'b', 'd'}
i expected the outputs for union and intersection to be the same for each. how is it possible that they are not? can anyone explain?
You cannot override the functionality of logical and and or in python. So when you call:
>>> set([1, 2, 3]) or set([2, 3, 4])
{1, 2, 3}
It's treating it as logical or, which would evaluate the left side to boolean true and immediately stops evaluating and returns the left side. Similarly:
>>> set([1, 2, 3]) and set([2, 3, 4])
{2, 3, 4}
Is treated as a logical and, which would evaluate the left side to boolean True and then evaluate the right side to boolean True resulting in the right side being returned.
Logical and and or have no relationship to bitwise & and | in any language, python included.
I guess it's better to illustrate with an example.
or returns the first value that evaluates as True
# any non-zero integer is True
1 or 0 => 1
0 or 1 or 2 => 1
0 or 0 or 2 => 2
since non-empty set x is evaluated as True
x or y => x which is {'d', 'b', 'e', 'c', 'a'}
Meanwhile and need to evaluate all the expressions and only when all the expressions are evaluated as True, it returns the last one.
1 and 2 => 2
1 and 'a' and (1, 2, 3) => (1, 2, 3)
since both x and y can be evaluated as True
x and y => y which is {'d', 'b', 'y', 'z', 'x'}
sets. This is howandandorwork for all types. Try1 or 2and50 or 0.x or yis not the same asx | y. The latter is the the union for sets. The former is saying return the first Truthy value.