Flask Request Object: Retrieving User Input and Parameters

Flask handles user request parameters through the `request` object, which must be imported from `flask` first. It mainly involves three scenarios: 1. **Query String (GET Parameters)**: Obtain parameters after the `?` in the URL using `request.args`, e.g., for `/hello?name=Alice`, use `get('参数名', default_value, type=type)`. This supports specifying parameter types (e.g., `type=int`). 2. **Form Data (POST)**: The route must specify `methods=['POST']`. HTML form data like `username` and `password` for a login form is retrieved via `request.form`. Ensure the frontend submits data in `application/x-www-form-urlencoded` format. 3. **JSON Data (POST)**: Parse JSON data with `request.get_json()`. First check if the request is JSON-formatted using `request.is_json`. `force=True` can be used to force parsing (not recommended). For example, receiving JSON data for user information. Key points: Clearly use the corresponding method for data types, use `get()` with default values to avoid errors, specify the method for POST requests, and consolidate knowledge through practice (e.g., squaring IDs, calculating JSON length).