How to pass arbitrary arguments to a flask blueprint?

Question

I have a flask api which I have wrapped up in an object. Doing this has made unit testing a breeze, because I can instantiate the api with a variety of different settings depending on whether it is in production, test, or whatehaveyou.

I am now trying to extend the api a bit, and for that I'm using a blueprint. The problem is that I cannot figure out how to pass arguments to the blueprint. My routes require information like which database to access, and that information is not static. How can I pass this information into a blueprint? I have included code below as an example:

api.py:

class MyApi(object):
    def __init__(self, databaseURI):
     self.app = Flask(__name__)
     self.app.register_blueprint(myblueprint)

blueprint.py

myblueprint= Blueprint('myblueprint', __name__)
@myblueprint.route('/route', methods=['GET'])
def route():
  database = OpenDatabaseConnection(databaseURI)

There is a related question here: How do I pass constructor arguments to a Flask Blueprint?

But the people who answer the question solve the op's use-case specific problem without actually answering the question of how to pass arbitrary arguments to a blueprint.

Answer 1

You could create the blueprint dynamically in a constructor function:

def construct_blueprint(database):

    myblueprint = Blueprint('myblueprint', __name__)

    @myblueprint.route('/route', methods=['GET'])
    def route():
        database = database

    return(myblueprint)

Answer 2

Use Flask config system (app.config) to store all your config data, then from your Blueprint read your Application Context using current_app.

Store in app.config:

app.config[DATABASE_URI] = databaseURI

Read application context:

databaseURI = current_app.config[DATABASE_URI]

Sample code

main.py

from flask import Flask
from blueprint import myblueprint

app = Flask(__name__)
app.register_blueprint(myblueprint)
app.config[DATABASE_URI] = databaseURI

blueprint.py

from flask import current_app

myblueprint= Blueprint('myblueprint', __name__)
@myblueprint.route('/route', methods=['GET'])
def route():
  databaseURI = current_app.config[DATABASE_URI]
  database = OpenDatabaseConnection(databaseURI)