<p>The way to define the Enum class in Python is to inherit the Enum base class and list the members; the enum value can be of any type; members can be accessed by name or value, but the values of different members cannot be repeated (unless IntEnum is used); ordinary Enum members can only judge equality, and IntEnum supports size comparison; Enum is often used to replace magic strings or numbers to improve code maintainability; enum classes cannot be instantiated, members are singletons and support traversal. For example, define Color(Enum): RED=1, GREEN=2, BLUE=3 or Status(Enum): PENDING='pending', SUCCESS='success', FAILED='failed'; use Color.RED or Color(2); when accessing; Color.RED == Color.GREEN is False; if you want to sort, you can use Rank(IntEnum): FIRST=1, SECOND=2; in actual development, if the order status OrderStatus(Enum) can be limited to the value of the parameter; in the framework, Enum can be automatically checksumed; use in to determine whether it exists, and traverse all members through members. </p> <p><img src="/static/imghw/default1.png" data-src="https://img.php.cn/upload/article/000/000/000/175286732121663.jpg" class="lazy" alt="Python Enum Class Usage"></p> <p> The Enum class is used in Python, mainly to define a set of named constants. Compared to hard-coded directly with numbers or strings, Enum makes the code clearer and easier to maintain, and can also avoid many low-level errors. </p> <img src="/static/imghw/default1.png" data-src="https://img.php.cn/upload/article/000/000/000/175286732217421.jpeg" class="lazy" alt="Python Enum Class Usage"><hr> <h3 id="How-to-define-an-Enum-class"> How to define an Enum class</h3> <p> Defining Enum is simple, you just need to inherit the <code>Enum</code> base class and list each member. Each member has a name and a value:</p><pre class='brush:php;toolbar:false;'> from enum import Enum class Color(Enum): RED = 1 GREEN = 2 BLUE = 3</pre><p> Here is a <code>Color</code> enumeration class that contains three constants: RED, GREEN and BLUE, corresponding to 1, 2, and 3, respectively. </p><img src="/static/imghw/default1.png" data-src="https://img.php.cn/upload/article/000/000/000/175286732424872.jpeg" class="lazy" alt="Python Enum Class Usage" /><p> Note: Enum values can be of any type, not necessarily integers. For example, it can also be written like this:</p><pre class='brush:php;toolbar:false;'> class Status(Enum): PENDING = &#39;pending&#39; SUCCESS = &#39;success&#39; FAILED = &#39;failed&#39;</pre><p> As long as you keep logically consistent, either way is OK. </p><img src="/static/imghw/default1.png" data-src="https://img.php.cn/upload/article/000/000/000/175286732617775.jpeg" class="lazy" alt="Python Enum Class Usage" /><hr /><h3 id="How-to-access-and-compare-Enum-members"> How to access and compare Enum members</h3><p> Enumeration members can be accessed by name:</p><pre class='brush:php;toolbar:false;'> print(Color.RED) # Output: Color.RED</pre><p> If you know the value, you can also get the enum member through the value:</p><pre class='brush:php;toolbar:false;'> print(Color(2)) # Output: Color.GREEN</pre><p> But it should be noted that different members cannot have the same value, otherwise an error will be reported (unless you are using <code>IntEnum</code> or <code>Flag</code> type).</p><p> Regarding comparison, the <code><</code> or <code>></code> comparison size cannot be used between ordinary Enum members, and can only determine whether it is equal:</p><pre class='brush:php;toolbar:false;'> Color.RED == Color.GREEN # False Color.RED is Color.RED # True</pre><p> If you really need sorting, you can consider inheriting <code>IntEnum</code> so that you can compare sizes:</p><pre class='brush:php;toolbar:false;'> from enum import IntEnum class Rank(IntEnum): FIRST = 1 SECOND = 2 Rank.FIRST < Rank.SECOND # True</pre><hr /><h3 id="How-to-use-Enum-in-actual-development"> How to use Enum in actual development</h3><p> The most common use of Enum is to replace magic strings or numbers, such as to represent states, types, configuration items, etc.</p><p> For example, when processing order status:</p><pre class='brush:php;toolbar:false;'> class OrderStatus(Enum): NEW = &#39;new&#39; PROCESSING = &#39;processing&#39; COMPLETED = &#39;completed&#39; CANCELLED = &#39;cancelled&#39; def process_order(status: OrderStatus): if status == OrderStatus.COMPLETED: print("Order Completed")</pre><p> This way, when passing parameters, it is limited to only using the defined state, and it is not easy to make mistakes.</p><p> In addition, in some frameworks (such as FastAPI, Django), Enum can also be automatically used for parameter checksum serialization output, which is very convenient.</p><hr /><h3 id="Some-details-that-are-easy-to-ignore"> Some details that are easy to ignore</h3><ul><li> <strong>Enumeration class cannot be instantiated</strong> : An error will be reported when trying to call <code>Color()</code> .</li><li> <strong>Enumeration members are singletons</strong> : the same enum value will only have one instance during the program's run.</li><li> <strong>You can use in to determine whether it exists</strong> :</li></ul><pre class='brush:php;toolbar:false;'> &#39;pending&#39; in Status.__members__.values() # False Color.RED in Color # True</pre><ul><li> <strong>The <strong>members</strong> property can traverse all members</strong> :</li></ul><pre class='brush:php;toolbar:false;'> for name, member in Color.__members__.items(): print(name, member)</pre><p> Basically that's it. Enum doesn't seem complicated, but it's very practical when organizing code structures, especially in multi-person collaboration projects, unified constant definition can save a lot of trouble.</p>

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