Possible Duplicate:
Absolute Beginner's Guide to Bit Shifting?
anyone can explain me that operator << or >>
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474answers:
4
+13
A:
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)
Gabi Purcaru
2010-10-12 18:46:43
Python isn't BASIC, so `a<<b` would be equivalent to `a*2**b` or `a*(2**b)` (and likewise for `>>`.
martineau
2010-10-12 19:02:20
-1 Think of `a << b` as `a * 2 ** b`
John Machin
2010-10-12 19:02:46
@martineau of course, I was trying to write it in a more readable format. But you are right. Modified.
Gabi Purcaru
2010-10-12 19:03:16
Might be better expressed as `a*pow(2,b)`.
martineau
2010-10-12 19:09:21
@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
2010-10-12 19:26:45
+3
A:
It's a shift operator.
http://docs.python.org/reference/expressions.html#shifting-operations
Júlio Santos
2010-10-12 18:47:11
+3
A:
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
2010-10-12 18:47:19
+25
A:
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
2010-10-12 18:47:22