Example of how to split a Flask blueprint into multiple files, with routes in each file, and of how to register all those routes.

bar.py

"""
Note: can't put in a subdirectory for this example (GitHub Gists
doesn't allow subdirectories). Recommended to move this file to
foo/bar.py.
"""


routes = []


def ping_bar():
    return 'Ping bar'


routes.append(dict(
    rule='/ping-bar/',
    view_func=ping_bar))


def save_bar():
    return 'Save bar'


routes.append(dict(
    rule='/save-bar/',
    view_func=save_bar,
    options=dict(methods=['POST',])))

baz.py

"""
Note: can't put in a subdirectory for this example (GitHub Gists
doesn't allow subdirectories). Recommended to move this file to
foo/baz.py.
"""


routes = []


def call_baz():
    return 'Call baz'


routes.append(dict(
    rule='/call-baz/',
    view_func=call_baz))


def delete_baz():
    return 'Delete baz'


routes.append(dict(
    rule='/delete-baz/',
    view_func=delete_baz,
    options=dict(methods=['GET', 'POST'])))

example_app.py

from flask import Flask


app = Flask(__name__)

app.debug = True


@app.route('/')
def home():
    return 'App home'


from foo import mod
app.register_blueprint(mod, url_prefix='/foo')


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

Flask-blueprint-with-imported-routes

*

foo.py

"""
Note: can't put in a subdirectory for this example (GitHub Gists
doesn't allow subdirectories). Recommended to move this file to
foo/__init__.py, and to change the imports to
'from .bar' and 'from .baz'.
"""


from flask import Blueprint


mod = Blueprint('foo', __name__)


@mod.route('/')
def home():
    return 'Foo home'


from bar import routes as bar_routes
from baz import routes as baz_routes


routes = (
    bar_routes +
    baz_routes)

for r in routes:
    mod.add_url_rule(
        r['rule'],
        endpoint=r.get('endpoint', None),
        view_func=r['view_func'],
        **r.get('options', {}))

requirements.txt

Flask==0.10.1

why don't you simply use Nesting Blueprints ? https://flask.palletsprojects.com/en/3.0.x/blueprints/#nesting-blueprints ?