Emulating Numeric types in Python

The following are the functions which can be defined to emulate numeric type objects. 

Methods to implement Binary operations on same type of objects :

These functions will make no change in the calling object rather they will return a new numeric object of same type after performing certain operation on the calling object. Following are the methods to implement arithmetic binary operations.

Method Operation
object.__add__(self, other) + (Addition)
object.__sub__(self, other) (Subtraction)
object.__mul__(self, other) * (Multiplication)
object.__matmul__(self, other) @ (Matrix multiplication)
object.__truediv__(self, other) / (True division)
object.__floordiv__(self, other) // (Floor division)
object.__mod__(self, other) % (Modulus or remainder)
object.__divmod__(self, other) divmod()
object.__pow__(self, other[, modulo]) ** (power)
object.__lshift__(self, other) << (Bit wise left shift)
object.__rshift__(self, other) >> (Bit wise right shift)
object.__and__(self, other) & (Bit wise AND operation)
object.__xor__(self, other) ^ (Exclusive OR operation)
object.__or__(self, other) | (Bit wise OR operation)

The __pow__() is defined to accept a third optional argument so as to support the ternary version of pow() function. Also if any of above method does not support the operation it should return NotImplemented .

Methods to implement Binary operations on different type of objects :

If type of object at left (collable object) is different then following methods can be used to perform arithmetic binary operations :

Method Operation
object.__radd__(self, other) + (Addition)
object.__rsub__(self, other) (Subtraction)
object.__rmul__(self, other) * (Multiplication)
object.__rmatmul__(self, other) @ (Matrix multiplication)
object.__rtruediv__(self, other) / (True division)
object.__rfloordiv__(self, other) // (Floor division)
object.__rmod__(self, other) % (Modulus or remainder)
object.__rdivmod__(self, other) divmod()
object.__rpow__(self, other[, modulo]) ** (pow() or power of number)
object.__rlshift__(self, other) << (Bit wise left shift)
object.__rrshift__(self, other) >> (Bit wise right shift)
object.__rand__(self, other) & (Bit wise AND operation)
object.__rxor__(self, other) ^ (Exclusive OR operation)
object.__ror__(self, other) | (Bit wise OR operation)

For example, if in a.__sub__(b), a is not of numeric type as of b then this method will return NotImplemented, then to perform a – b we will call a.__rsub__(b).



Methods to implement arithmetic assignment operations :

These methods are used to implement the arithmetic assignment operations. They will not return a new object rather they will assign the new value in calling object itself. Like x.__imul__(y) will be performed as x = x * y. Following are the corresponding operations to each method.

Method Operation
object.__iadd__(self, other) += (Addition assignment)
object.__isub__(self, other) -= (Subtraction assignment)
object.__imul__(self, other) *= (Multiplication assignment)
object.__imatmul__(self, other) @= (Matrix multiplication assignment)
object.__itruediv__(self, other) /= (True division assignment)
object.__ifloordiv__(self, other) //= (Floor division assignment)
object.__imod__(self, other) %= (Modulus or remainder assignment)
object.__ipow__(self, other[, modulo]) **= (power of number assignment)
object.__ilshift__(self, other) <<= (Bit wise left shift assignment)
object.__irshift__(self, other) >>= (Bit wise right shift assignment)
object.__iand__(self, other) &= (Bit wise AND operation assignment)
object.__ixor__(self, other)  ^= (Exclusive OR operation assignment)
object.__ior__(self, other) |= (Bit wise OR operation assignment)

Methods to implement unary arithmetic operations :

Following are the methods to implement unary arithmetic operations like, negative of a number, inverse of a number etc.

Method Operation
object.__neg__(self) (unary minus)
object.__pos__(self) + (unary plus)
object.__abs__(self) abs() in-built function
object.__invert__(self) ~ (complement of a number)

Some other important methods :

Method Description
object.__index__(self)

Called to implement operator.index() function, also used to convert a numeric type object to integer type,  

or we can say if __int__(), __float__() or __complex__() is not defined then int(), float() and complex() falls 

under __index__().

object.__round__(self, ndigits)

To implement the round() function, the second optional argument tells up to how many decimal places 

we want to round the numeric value.

object.__trunc__(self) To implement trunc() function.
object.__floor__(self) To implement floor() function.
object.__ceil__(self) To implement ceil() function.

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