My flask application currently consists of a single test.py file with multiple routes and the main() route defined. Is there some way I could create a test2.py file that contains routes that were not handled in test.py?

@app.route('/somepath')
def somehandler():
    # Handler code here

I am concerned that there are too many routes in test.py and would like to make it such that I can run python test.py, which will also pick up the routes on test.py as if it were part of the same file. What changes to I have to make in test.py and/or include in test2.py to get this to work?

You can use the usual Python package structure to divide your App into multiple modules, see the Flask docs.

However,

Flask uses a concept of blueprints for making application components and supporting common patterns within an application or across applications.

You can create a sub-component of your app as a Blueprint in a separate file:

simple_page = Blueprint('simple_page', __name__, template_folder='templates')
@simple_page.route('/<page>')
def show(page):
    # stuff

And then use it in the main part:

from yourapplication.simple_page import simple_page

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

Blueprints can also bundle specific resources: templates or static files. Please refer to the Flask docs for all the details.