[Python] Add [<ClassAttributes>] to control Python class generation

src/Fable.Cli/CHANGELOG.md

@@ -7,6 +7,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## Unreleased
 
+### Added
+
+* [Python] Added `ClassAttributes` attribute to control Python class generation (@dbrattli)
+
 ### Fixed
 
 * [TS/Dart] Fixed optional parameter types (by @ncave)
@@ -105,14 +109,14 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 * [Python] Fix date formatting when repeating a format token more than the known format (example repeating 'd' more than 4 times) (by @MangelMaxime)
 * [JS/TS] Fix #4010: Supports direct nested types when using `jsOptions` (by @MangelMaxime)
 
-    ```fs
+```fs
     let opts =
         jsOptions<Level1> (fun o ->
             o.level2.level3.valueA <- 10
             o.level2.level3.valueB <- 20
             o.topValueA <- 20
         )
-    ```
+```
 
 * [JS/TS] Fix numeric formats (by @MangelMaxime)
 

src/Fable.Core/CHANGELOG.md

@@ -7,6 +7,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## Unreleased
 
+### Added
+
+* [Python] Added `ClassAttributes` attribute to control Python class generation (@dbrattli)
+
 ## 5.0.0-beta.1 - 2025-07-25
 
 ### Added

src/Fable.Core/Fable.Core.Py.fs

@@ -27,6 +27,22 @@ module Py =
 
         abstract Decorate: fn: Callable * info: Reflection.MethodInfo -> Callable
 
+    /// <summary>
+    /// Used on a class to provide Python-specific control over how F# types are transpiled to Python classes.
+    /// This attribute implies member attachment (similar to AttachMembers) while offering Python-specific parameters.
+    /// </summary>
+    /// <remarks>
+    /// <para>When placed on a class, all members are attached without mangling (like AttachMembers).</para>
+    /// <para>Additional Python-specific parameters control the generated Python class style and features.</para>
+    /// </remarks>
+    [<AttributeUsage(AttributeTargets.Class)>]
+    type ClassAttributes() =
+        inherit Attribute()
+
+        new(style: string) = ClassAttributes()
+
+        new(style: string, init: bool) = ClassAttributes()
+
     // Hack because currently Fable doesn't keep information about spread for anonymous functions
     [<Emit("lambda *args: $0(args)")>]
     let argsFunc (fn: obj[] -> obj) : Callable = nativeOnly

src/Fable.Transforms/FSharp2Fable.Util.fs

@@ -2106,6 +2106,7 @@ module Util =
             // Should we make sure the attribute is not an alias?
             match att.AttributeType.TryFullName with
             | Some Atts.attachMembers -> true
+            | Some Atts.pyClassAttributes -> true
             | _ -> false
         ))