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Programming in Python

Operator Overloading

Explore how to define custom behaviors for common operators in Python classes through operator overloading. Learn to implement special methods such as __add__, __sub__, and __eq__ to enable intuitive operations on objects. Understand the list of overloadable operators and the unique aspect that Python does not support function overloading.

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Common operators are used for their predefined purpose and functionality. When we intend to use them for an additional purpose, we need to explicitly define their behavior for a particular class. This phenomenon is called operator overloading.

Since Complex is a user-defined class, Python doesn’t know how to add objects to this class. We can teach it how to do that by overloading the +, -, +=, and == operators, as shown below:

Python 3.8
class Complex :
  def __init__(self, r = 0.0, i = 0.0) :
    self.__real = r
    self.__imag = i
  
  def __add__(self, other) :
    z = Complex( )
    z.__real = self.__real + other.__real
    z.__imag = self.__imag + other.__imag
    return z
  def __sub__(self, other) :
    z = Complex( )
    z.__real = self.__real - other.__real
    z.__imag = self.__imag - other.__imag
    return z
  def __iadd__(self, other) :
    z = Complex( )
    z.__real = self.__real + other.__real
    z.__imag = self.__imag + other.__imag
    return z
  
  def __eq__(self, other):
    real = self.__real == other.__real
    imag = self.__imag == other.__imag
    return (real == True & imag == True)
  def display(self) :
    print(self.__real, self.__imag)
c1 = Complex(1.1, 0.2)
c2 = Complex(1.1, 0.2)
c3 = c1 + c2
c3.display( )
c4 = c1 - c2
c4.display( )
c1 = Complex(1.1, 0.2)
c2 = Complex(1.1, 0.2)
c1 += c2
c1.display( )
if c3 == c1:
  print('Both complex numbers are equal.')
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