The Python bitwise left-shift operator
x << n shifts the binary representation of integer
n positions to the left. For a positive integer, it inserts a
0 bit on the right and shifts all remaining bits by one position to the left. For example, if you left-shift the binary representation
0101 by one position, you’d obtain
01010. Semantically, the bitwise left-shift operator
x << n is the same as multiplying the integer
Here’s a minimal example:
print(8 << 1) # 16 print(8 << 2) # 32 print(-3 << 1) # -6
Let’s dive deeper into the details next!
As you go over the article, you can watch my explainer video here:
In this example, you apply the bitwise left-shift operator to integer 32 shifting it by one position:
x = 32 # Shift by one position to the left res = x << 1 print(res) # 64 # Shift by two positions to the left res = x << 2 print(res) # 128
The bit representation of decimal
"0100000". If you shift it by one position to the left, you obtain binary
" (decimal 64). If you shift by two positions to the right, you obtain binary
" (decimal 128). Here’s the tabular explanation:
Each row represents the resulting shifted binary representation of the original integer 32.
Python Bitwise Left-Shift Operator Overloading
To enable the left-shift operator on your custom object, use Python’s operator overloading functionality. Overloading works through what is called magic methods or dunder methods (for “double-underscore methods”). For the left-shift operator, the magic method is the
__lshift__(self, other) method. It should return a new custom object that is the result of the bitwise operation.
Here’s a short overview of the Bitwise operators’ magic methods:
|Bitwise Operator||Magic “Dunder” Method|
Here’s an example of how to accomplish these bitwise operators on a custom class
Data. We marked this respective operator in the code:
class Data: def __init__(self, data): self.data = data def __and__(self, other): return Data(self.data & other.data) def __or__(self, other): return Data(self.data | other.data) def __xor__(self, other): return Data(self.data ^ other.data) def __invert__(self): return Data(~self.data) def __lshift__(self, other): return Data(self.data << other.data) def __rshift__(self, other): return Data(self.data >> other.data) x = 2 y = 3 print('Operands: \n', 'x =', x, '\n', 'y =', y) print() print('Bitwise AND: ', x & y) print('Bitwise OR: ', x | y) print('Bitwise XOR: ', x ^ y) print('Bitwise NOT: ', ~x) print('Bitwise LEFT-SHIFT: ', x << y) print('Bitwise RIGHT-SHIFT: ', x >> y)
The output is:
Operands: x = 2 y = 3 Bitwise AND: 2 Bitwise OR: 3 Bitwise XOR: 1 Bitwise NOT: -3 Bitwise LEFT-SHIFT: 16 Bitwise RIGHT-SHIFT: 0
Bitwise operators perform operations on the binary (bit) representation of integers. The following table gives a short overview of all existing bitwise operators. Note that we also provide the binary representation
100 for the decimal integer
101 for the decimal integer
5 as a comment in the right column.
|&||Bitwise AND||Performs logical AND on a bit-by-bit basis|
||||Bitwise OR||Performs logical OR operation on a bit-by-bit basis|
|~||Bitwise NOT||Performs logical NOT on a bit-by-bit basis, inverting each bit so that 0 becomes 1 and 1 becomes 0. Same as |
|^||Bitwise XOR||Performs logical “exclusive or” operation on a bit-by-bit basis|
|>>||Bitwise right shift||Shifts binary of left operand to the right by the number of positions specified in right operand|
|<<||Bitwise left shift||Shifts binary of left operand to the left by the number of positions specified in right operand|
While working as a researcher in distributed systems, Dr. Christian Mayer found his love for teaching computer science students.
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