routing a view through blueprint in another module doesn't work

Question

I have a flask project with following three files:

# app.py

from flask import Flask

from userbp import bp

app =  Flask(__name__)
app.register_blueprint(bp)

@app.route("/")
def index():
    return "Hello, world"

# userbp.py
from flask import Blueprint


bp = Blueprint("user", __name__, url_prefix="/user")

# user_views.py

from userbp import bp


@bp.route("/<string:name>")
def greet(name):
    return f"Hello, {name}! How are you?"

Here is the structure of this project's root directory:

.
├── __pycache__
│   ├── app.cpython-311.pyc
│   └── userbp.cpython-311.pyc
├── app.py
├── user_views.py
└── userbp.py

It is not working as expected, hitting the URL /John gives a 494 not found error. While if I move the greet view from user_views.py to userbp.py, it works as expected. Why is it so? How to fix this problem?

TYPO: It was actually 404 error Thanks.

Answer 1

There a 2 solutions for this problem.

• Best practices for blueprint in flask is that sub-route should define with same as blueprint initiations.

So your code should be like this

# app.py
from flask import Flask

# import blueprint from userbp.py
from userbp import bp

app = Flask(__name__)

app.register_blueprint(bp)


@app.route("/")
def index():
    return "Hello, world"


if __name__ == "__main__":
    app.run()

# userbp.py

from flask import Blueprint

# initialization of blueprint
bp = Blueprint("user", __name__, url_prefix="/user")

## implementation of sub-route blueprints
@bp.route("/<string:name>")
def greet(name):
    return f"Hello, {name}! How are you?"

• If you still want to separate initialization of blueprint and the implementation of sub-route you can do like this.

# app.py

from flask import Flask

# import blueprint from user_views.py
from user_views import bp

app = Flask(__name__)

app.register_blueprint(bp)


@app.route("/")
def index():
    return "Hello, world"


if __name__ == "__main__":
    app.run()

# userbp.py

from flask import Blueprint


bp = Blueprint("user", __name__, url_prefix="/user")

# user_views.py

from userbp import bp


@bp.route("/<string:name>")
def greet(name):
    return f"Hello, {name}! How are you?"

So like this will work.

And the problem, why it's show error not found cause you accessing the wrong routes.

It Should be like this http://localhost:5000/user/john. Cause in blueprint your code is defined to sub-route user

in here

bp = Blueprint("user", __name__, url_prefix="/user")