How to implement operator overloading in Python (e.g., __add__, __sub__)?

<p>How to effectively implement operator overloading in Python? 1. Define special methods (such as __add__, __sub__) in the class to specify operator behavior. For example, use __add__ in the Vector class to implement vector addition and return a new instance; 2. To support the situation where the object is on the right side of the operation, it is necessary to define methods such as __radd__, __rsub__, etc.; 3. Other common operators such as __mul__, __eq__, __lt__, etc. can be overloaded to extend functions; 4. Pay attention to handling type checks and return value consistency to ensure interaction reliability. </p> <p><img src="/static/imghw/default1.png" data-src="https://img.php.cn/upload/article/000/000/000/175217215270198.jpg" class="lazy" alt="How to implement operator overloading in Python (e.g., __add__, __sub__)?"></p> <p> Sure, operator overloading in Python is a powerful feature that lets you define how operators like<code> </code>, <code>-</code> , <code>==</code> , etc., behave for instances of your custom classes. It's done by defining special methods (also known as magic or dunder methods) in your class. </p> <img src="/static/imghw/default1.png" data-src="https://img.php.cn/upload/article/000/000/000/175217215341442.jpeg" class="lazy" alt="How to implement operator overloading in Python (e.g., __add__, __sub__)?"><p> Let's walk through how to implement it effectively using common examples like <code>__add__</code> and <code>__sub__</code> .</p> <hr> <h3> Overloading the<code> </code>Operator with <code>__add__</code> </h3> <p> To use the<code> </code>operator with your own objects, you need to define the <code>__add__</code> method in your class. This tells Python what should happen when you do something like <code>obj1 obj2</code> . </p> <img src="/static/imghw/default1.png" data-src="https://img.php.cn/upload/article/000/000/000/175217215567658.jpeg" class="lazy" alt="How to implement operator overloading in Python (e.g., __add__, __sub__)?"><p> For example, imagine you have a <code>Vector</code> class:</p><pre class='brush:php;toolbar:false;'> class Vector: def __init__(self, x, y): self.x = x self.y = y def __add__(self, other): return Vector(self.x other.x, self.y other.y)</pre><p> Now you can add two vectors like this: </p><img src="/static/imghw/default1.png" data-src="https://img.php.cn/upload/article/000/000/000/175217215776341.jpeg" class="lazy" alt="How to implement operator overloading in Python (e.g., __add__, __sub__)?" /><pre class='brush:php;toolbar:false;'> v1 = Vector(1, 2) v2 = Vector(3, 4) v3 = v1 v2 # Uses __add__</pre><p> A few things to note:</p><ul><li> Make sure the <code>other</code> object has the expected attributes.</li><li> Return a new instance instead of modifying the existing ones unless you have a good reason not to.</li><li> You can also handle type checking inside <code>__add__</code> if needed.</li></ul><hr /><h3 id="Overloading-the-code-code-Operator-with-code-sub-code"> Overloading the <code>-</code> Operator with <code>__sub__</code></h3><p> Just like <code>__add__</code> , you can define <code>__sub__</code> to support subtraction.</p><p> Here's how you might do it in the same <code>Vector</code> class:</p><pre class='brush:php;toolbar:false;'> def __sub__(self, other): return Vector(self.x - other.x, self.y - other.y)</pre><p> Then subtracting becomes straightforward:</p><pre class='brush:php;toolbar:false;'> v3 = v2 - v1</pre><p> This works similarly to addition:</p><ul><li> Assumes <code>other</code> has <code>.x</code> and <code>.y</code></li><li> Returns a new <code>Vector</code> instance</li></ul><p> If you try to subtract an incompatible type, Python will raise an error — so you may want to include a check:</p><pre class='brush:php;toolbar:false;'> if not isinstance(other, Vector): raise TypeError("Can only subtract another Vector")</pre><hr /><h3 id="Handling-Reverse-Operations-with-code-radd-code-code-rsub-code-etc"> Handling Reverse Operations with <code>__radd__</code> , <code>__rsub__</code> , etc.</h3><p> What happens if someone tries to do <code>5 Vector(1, 2)</code> ? Since <code>int.__add__</code> doesn't know how to handle a <code>Vector</code> , Python checks whether <code>Vector.__radd__</code> exists.</p><p> So if you want expressions where your object appears on the right-hand side to work, define <code>__radd__</code> , <code>__rsub__</code> , and others.</p><p> Example:</p><pre class='brush:php;toolbar:false;'> def __radd__(self, other): # Assume other is a scalar or int return Vector(self.x other, self.y other)</pre><p> You don't always need these, but they're useful if you want more flexibility in how your objects interact with built-in types.</p><hr /><h3 id="Other-Commonly-Overloaded-Operators"> Other Commonly Overloaded Operators</h3><p> You're not limited to just<code> </code>and <code>-</code> . Here are some other handy ones:</p><ul><li> <code>__mul__</code> and <code>__rmul__</code> – for multiplication ( <code>*</code> )</li><li> <code>__eq__</code> – for equality comparison ( <code>==</code> )</li><li> <code>__lt__</code> – for less-than comparison ( <code><</code> )</li><li> <code>__str__</code> or <code>__repr__</code> – for string representation (not an operator, but often used alongside)</li></ul><p> For example, to compare two vectors:</p><pre class='brush:php;toolbar:false;'> def __eq__(self, other): return self.x == other.x and self.y == other.y</pre><p> Then you can do:</p><pre class='brush:php;toolbar:false;'> v1 == v2 # returns True or False</pre><hr> <p> That's basically how you implement and use operator overloading in Python. It's not complicated, but it does require attention to detail — especially around handling different types and ensuring consistent return values.</p>

The above is the detailed content of How to implement operator overloading in Python (e.g., __add__, __sub__)?. For more information, please follow other related articles on the PHP Chinese website!