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In-Depth Python OOP

bookComparison Magic Methods

Similarly to the mathematical magic methods, here we take self and other as arguments and compare their desired attributes. These magic methods should always return True or False.

Magic MethodOperation
__eq__(self, other)==
__gt__(self, other)>
__ge__(self, other)>=
__lt__(self, other)<
__le__(self, other)<=
__ne__(self, other)!=

Note

To understand the naming of these methods, look at some examples:

  • eq is equal.
  • gt is greater than.
  • le is less or equal.
  • ne is not equal.

              
12345

            
a = 12.3
b = 5.7

print("a >= b is", a >= b)
print("a.__ge__(b) is", a.__ge__(b))
copy

Look at the example of Road class:


              
123456789101112131415161718

            
class Road:
    def __init__(self, length):
        self.length = length

    def __eq__(self, other):
        if isinstance(other, Road):
            return self.length == other.length  # compare with road
        return self.length == other  # compare with number

road_1 = Road(20)
road_2 = Road(30)
road_3 = Road(20)

print(road_1 == road_2)
print(road_1 == road_3)
print(road_1 == 20)
print(road_1 == 20.0)
print(road_1 == 1412)
copy

Note

To optimize the code, you can utilize existing comparison methods. For example, if you have implemented the __lt__() method (<), by implementing the __ge__() method (>=), you can use return not (instance1 < instance2) which will return the opposite result of the already implemented < operator.

question mark

Which magic method should be used?

Select the correct answer

Var allt tydligt?

Hur kan vi förbättra det?

Tack för dina kommentarer!

Avsnitt 5. Kapitel 4

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bookComparison Magic Methods

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Similarly to the mathematical magic methods, here we take self and other as arguments and compare their desired attributes. These magic methods should always return True or False.

Magic MethodOperation
__eq__(self, other)==
__gt__(self, other)>
__ge__(self, other)>=
__lt__(self, other)<
__le__(self, other)<=
__ne__(self, other)!=

Note

To understand the naming of these methods, look at some examples:

  • eq is equal.
  • gt is greater than.
  • le is less or equal.
  • ne is not equal.

              
12345

            
a = 12.3
b = 5.7

print("a >= b is", a >= b)
print("a.__ge__(b) is", a.__ge__(b))
copy

Look at the example of Road class:


              
123456789101112131415161718

            
class Road:
    def __init__(self, length):
        self.length = length

    def __eq__(self, other):
        if isinstance(other, Road):
            return self.length == other.length  # compare with road
        return self.length == other  # compare with number

road_1 = Road(20)
road_2 = Road(30)
road_3 = Road(20)

print(road_1 == road_2)
print(road_1 == road_3)
print(road_1 == 20)
print(road_1 == 20.0)
print(road_1 == 1412)
copy

Note

To optimize the code, you can utilize existing comparison methods. For example, if you have implemented the __lt__() method (<), by implementing the __ge__() method (>=), you can use return not (instance1 < instance2) which will return the opposite result of the already implemented < operator.

question mark

Which magic method should be used?

Select the correct answer

Var allt tydligt?

Hur kan vi förbättra det?

Tack för dina kommentarer!

Avsnitt 5. Kapitel 4
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