http://graphics.stanford.edu/~seander/bithacks.html#DetermineIfPowerOf2 You have many useful bit hacks here.
Visar Zejnullahu On Sat, Sep 1, 2012 at 1:17 AM, Visar Zejnullahu <visar.zejnull...@gmail.com > wrote: > 2^n in binary is 10...0 (with n 0s), and 2^n - 1 is 11...1 (with n 1s). So > if you do bitwise and (&) to 2^n and 2^n-1 you get all 0s. That's why you > check if (num & (num - 1)) == 0. > > Visar Zejnullahu > > > > On Sat, Sep 1, 2012 at 12:54 AM, Lazar <chaost...@gmail.com> wrote: > >> Hello, >> >> I'm fairly new to Python and still learning. >> >> Can someone please explain to me in what way the following function >> checks if a number is a power of two? Basically, the second line of >> code is what I can't really grasp: >> >> def is_power2(num): >> return num != 0 and ((num & (num - 1)) == 0) >> >> Thank you, >> Lazar >> _______________________________________________ >> Tutor maillist - Tutor@python.org >> To unsubscribe or change subscription options: >> http://mail.python.org/mailman/listinfo/tutor >> > >
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