Advanced FastAPI Path Parameters: Dynamic Routing and Parameter Validation

FastAPI supports dynamic routing and parameter validation with flexibility and robustness. Basic usage includes paths like `/users/{user_id}`, where parameters can be automatically type-identified (e.g., `int`), and conversion failures return a 422 error. For advanced dynamic routing, it supports automatic type conversion, optional parameters (`Optional` with default values), and regex restrictions (`Path.pattern`), such as for order codes requiring an 8-character combination of uppercase letters/numbers (`^[A-Z0-9]{8}$`). Advanced parameter validation is achieved by setting ranges (`ge`/`le`) via `Path` or using enumeration types, e.g., product IDs must be `ge=1, le=99`, and order types restricted to the enum values `pending/completed/cancelled`. By combining dynamic routing with validation, a general interface is constructed, reducing manual validation code. The Swagger documentation (`/docs`) allows intuitive testing of these rules.