__ixor__() magic method implements the in-place bitwise XOR
x ^= y that calculates the result of the bitwise XOR operation
x ^ y, and assigns it to the first operands’ variable
x. This type of in-place operation is also called augmented arithmetic assignment. The method simply returns the new value to be assigned to the first operand.
- When you call
x ^= y, Python first attempts to call
- If this is not implemented, it tries the normal bitwise AND operation
- If this is not implemented either, it tries reverse exponentiation operation
y.__rxor__(x)with swapped operands.
The result is then assigned to the first operand
x. If none of those operations is implemented, Python raises a
We call this a “Dunder Method” for “Double Underscore Method” (also called “magic method”). To get a list of all dunder methods with explanation, check out our dunder cheat sheet article on this blog.
Basic Example Overriding __ixor__
In the following code example, you create a class
Data and define the magic method
- The “self” argument is the default argument of each method and it refers to the object on which it is called—in our case, the first operand of the in-place operation.
- The “other” argument of the in-place method refers to the second operand, i.e.,
yin the in-place operation
x ^= y.
The return value of the operation returns a dummy string
'finxter 42' to be assigned to the first operand. In practice, this would be the result of the in-place bitwise XOR operation.
class Data: def __ixor__(self, other): return 'finxter 42' x = Data() y = Data() x ^= y print(x) # finxter 42
In-Place XOR ^= without __ixor__()
To support the in-place bitwise XOR operation on a custom class, you don’t have to overwrite the
__ixor__() method. Because if the method is not defined, Python will fall back to the normal
__xor__() method and assign its result to the first operand.
Here’s an example:
class Data: def __xor__(self, other): return 'finxter 42' x = Data() y = Data() x ^= y print(x) # finxter 42
Even though the
__ixor__() method is not defined, the in-place bitwise XOR operation
x ^= y still works due to the
__xor__() “fallback” magic method!
In-Place XOR ^= without __ixor__() and __xor__()
To support in-place bitwise XOR
x ^= y on a custom class, you don’t even have to overwrite any of the
x.__xor__(y) methods. If both are not defined, Python falls back to the reverse
y.__rxor__(x) method and assigns its result to the first operand.
Here’s an example where you create a custom class for the first operand that doesn’t support the bitwise XOR operation. Then you define a custom class for the second operand that defines the
__rxor__() method. For the in-place operation, Python falls back to the
__rxor__() method defined on the second operand and assigns it to the first operand
class Data_1: pass class Data_2: def __rxor__(self, other): return 'finxter 42' x = Data_1() y = Data_2() x ^= y print(x) # finxter 42
TypeError: unsupported operand type(s) for ^=
If you try to perform in-place bitwise OR
x ^= y but neither
y.__rxor(x) is defined, Python raises a “
TypeError: unsupported operand type(s) for ^=". To fix this error, simply define any of those methods before performing the in-place operation.
class Data: pass # ... you should define __ixor__ here to prevent error! ... # x = Data() y = Data() x ^= y
Traceback (most recent call last): File "C:\Users\xcent\Desktop\code.py", line 8, in <module> x ^= y TypeError: unsupported operand type(s) for ^=: 'Data' and 'Data'
Background Bitwise XOR
Python’s bitwise XOR operator
x ^ y performs logical XOR on each bit position on the binary representations of integers
y. Each output bit evaluates to 1 if and only if exactly one of the two input bits at the same position are 1.
For example, the integer expression
4 ^ 3 is translated to the binary operation
0100 ^ 0011 which results in
0111 because for the last three positions exactly one bit is 1.
You can learn more in our in-depth tutorial on this operator:
Related Video Compound Operators
Where to Go From Here?
Enough theory. Let’s get some practice!
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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.
His passions are writing, reading, and coding. But his greatest passion is to serve aspiring coders through Finxter and help them to boost their skills. You can join his free email academy here.