Flask Blueprint Object API
Blueprint is used to split an application into reusable modules. Each blueprint can have its own routes, templates, static files, and hooks.
Creation method:
bp = Blueprint("auth", __name__)
Constructor parameters
| Parameter | Type | Default value | Description |
|---|---|---|---|
| name | str | Required | Blueprint name, used for the endpoint prefix in url_for |
| import_name | str | Required | The module name where the blueprint resides, used to locate resources. Usually pass __name__. |
| static_folder | str | None | Blueprint static file folder |
| static_url_path | str | None | The URL path at which static files are exposed. |
| template_folder | str | None | Blueprint template folder |
| url_prefix | str | None | A common prefix for all routes in the blueprint, e.g., "/auth". |
| subdomain | str | None | Subdomain matched by blueprint routes |
| url_defaults | dict | None | Default URL parameters for blueprint routes |
| root_path | str | None | Blueprint root path, usually auto-discovered |
| cli_group | str | None | The CLI command group name. Uses the blueprint name by default. |
Core attributes
| Property | Type | Description |
|---|---|---|
| name | str | Blueprint name, used as the endpoint prefix after registration |
| cli | AppGroup | The blueprint-specific CLI command group, where custom commands can be added. |
| has_static_folder | bool | Whether a static folder is configured |
Route methods
The usage of blueprints is the same as a Flask application, exceptappReplace withbp：
| Methods | Description |
|---|---|
| route(rule, **options) | Decorator that binds a URL to a view function. |
| get / post / put / delete / patch(rule, **options) | HTTP method shortcut decorators |
| add_url_rule(rule, endpoint, view_func, **options) | Adding URL rules programmatically |
Hook decorator
The blueprint's hooks only affect routes within the blueprint:
| Methods | Description |
|---|---|
| before_request | Execute before all requests within the blueprint |
| after_request | Execute after the request response within the blueprint |
| teardown_request | Execute when the request context is destroyed within the blueprint |
| errorhandler(code_or_exception) | Error handlers within the blueprint |
| url_value_preprocessor | URL value preprocessors within the blueprint |
| url_defaults | Default URL parameters within the blueprint |
| template_filter / template_test / template_global | Blueprint template filters / tests / global functions. |
Blueprint-specific methods
| Methods | Description |
|---|---|
| register(app, options) | Register the blueprint to the Flask application. Called internally by app.register_blueprint() |
| record(func) | Register a callback function that is called when the blueprint is registered to the application |
| record_once(func) | Same as record, but executed only once when the blueprint is registered multiple times |
| make_setup_state(app, options) | Create blueprint registration state object |
| send_static_file(filename) | Send a file from the blueprint's static folder |
| open_resource(resource, mode="rb") | Open a resource file under the blueprint's root path |
Options parameters when registering the blueprint
Callapp.register_blueprint(bp, **options)When calling, you can pass:
| Parameter | Description |
|---|---|
| url_prefix | Override the blueprint's URL prefix |
| subdomain | Override the blueprint's subdomain |
| url_defaults | Override the blueprint's URL defaults |
| name | Rename the blueprint (the same blueprint can be registered multiple times, each time with a different name) |
Code Examples
Example
from flask import Blueprint, render_template
# Create blueprint
bp = Blueprint("blog", __name__,
url_prefix="/blog",
template_folder="templates",
static_folder="static")
# Register routes
@bp.route("/")
def index():
return render_template("blog/index.html")
@bp.route("/<int:post_id>")
def show(post_id):
return f"Show post {post_id}"
# Blueprint hooks
@bp.before_request
def check_login():
# Only applies to /blog/* routes
pass
# Register in the app
# app.register_blueprint(bp)
# Create blueprint
bp = Blueprint("blog", __name__,
url_prefix="/blog",
template_folder="templates",
static_folder="static")
# Register routes
@bp.route("/")
def index():
return render_template("blog/index.html")
@bp.route("/<int:post_id>")
def show(post_id):
return f"Show post {post_id}"
# Blueprint hooks
@bp.before_request
def check_login():
# Only applies to /blog/* routes
pass
# Register in the app
# app.register_blueprint(bp)