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Why (x and y) == y ? Why (x or y) == x ?
x, y have any types. (x and y) always equals y (except when x==0) (x or y) always equals x (even if y == True) Why?
3 odpowiedzi
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In Python logical operators won't convert results into booleans, but have certain logics to return either of the operands.
Easy way would be to compare them to equivalent ternary operators:
A and B: A if not A else B
A or B: A if A else B
In words:
A and B:
Returns A, if bool(A) is False, otherwise it returns B.
A or B:
Returns A, if bool(A) is True, otherwise it returns B.
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Because when comparing x and y (with the "and" operator), you are forcing python to convert them to boolean.
Python considers all numbers/characters to be true, except for 0.
Therefore, if you compare any two numbers with "and", it will give you true unless one of them is 0/False (that's how "and" works).
And when you compare them with "or", it will be enough for one of them to be a number/character in order for the statement to be all true (that's how "or" works").
Good Luck.
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Thanks. Your answer is very logical, but try, please, following:
z = "abc" and [1,2]
print(z)
You'll get [1,2] but not True. Python gives result without conversion to boolean.
z = "abc" or True
print(z)
abc
It's really funny, but hard for user's brain