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Absolute Beginner's Guide to Bit Shifting?
anyone can explain me that operator << or >>
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The << and >> operators are bitshift operators. x << 1 shifts all the bits in x up to the next most significant bit, effectively multiplying by 2. More generally, x << n shifts the bits up n positions. To understand how this operation works it is easiest to look at the binary representation:
3 0000011 = 3
3 << 1 0000110 = 6
3 << 2 0001100 = 12
3 << 3 0011000 = 24
Similarly the >> operator shifts the bits down:
58 0111010 = 58
58 >> 1 0011101 = 29
58 >> 2 0001110 = 14
58 >> 3 0000111 = 7
58 >> 4 0000011 = 3
58 >> 5 0000001 = 1
58 >> 6 0000000 = 0
Mark Byers
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3, in binary, is 11 and shifted to left one bit is 110, or 6 in decimal.
Think of a << b as a * (2 ** b)
>> is for right-shifting. Think of a >> b as a // (2 ** b)
John Machin
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Gabi Purcaru
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Python isn't BASIC, so `a<>`. – martineau Oct 12 '10 at 19:02
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-1 Think of `a << b` as `a * 2 ** b` – John Machin Oct 12 '10 at 19:02
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@martineau of course, I was trying to write it in a more readable format. But you are right. Modified. – Gabi Purcaru Oct 12 '10 at 19:03
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Might be better expressed as `a*pow(2,b)`. – martineau Oct 12 '10 at 19:09
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1@John Machin - Thanks for including the use of `//`. I think a lot of people are going to be surprised that `/` always means floating point division in Python3. – Omnifarious Oct 12 '10 at 19:26
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It's a shift operator.
http://docs.python.org/reference/expressions.html#shifting-operations
Julio Santos
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It's a bit shift, using a shifting operation.
Say you have a number, and looking at the lowest bits, you have 3:
0 0 1 1
If you shift it, you'll get 6, or:
0 1 1 0
Reed Copsey
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