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Mark Chesney
11,747 Pointsbitwise not operator: tilde vs minus sign (~ vs -)
I didn't notice there being any difference between ~ and - used for negating an index. For example:
no_referrals_index = users.referral_count < 1
~no_referrals_index
users[~no_referrals_index]
-no_referrals_index
users[-no_referrals_index]
Just an observation. Am I wrong?
2 Answers
Mark Chesney
11,747 PointsYes, I'm coming from the context of this exercise, using these operators on pandas series, as inputs into a data frame, rather than the discrete math examples
Steven Parker
229,732 PointsYour example doesn't show what the values being used are, but there should be a difference.
Since integers are stored in "two's complement notation", -0 (minus 0) is still 0, but ~0 (bitwise not 0) is -1. Similarly, the bitwise inverse of any positive integer will be the negative of the next larger number.
Steven Parker
229,732 PointsAnother peculiarity is that these operators are being applied to a boolean value resulting from a comparison. But when you coerce it into an integer, the two's complement rules still apply. So when no_referrals_index is True, The negative will be -1 and the bitwise inverse will be -2. When it is False, the negative will be 0 and the bitwise inverse will be -1.