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.
To help students reach higher levels of Python success, he founded the programming education website Finxter.com. He’s author of the popular programming book Python One-Liners (NoStarch 2020), coauthor of the Coffee Break Python series of self-published books, computer science enthusiast, freelancer, and owner of one of the top 10 largest Python blogs worldwide.
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