What's the right approach for calling functions after a flask app is run?
Solution 1
The duplicate output from your function can be explained by the reloader. The first thing it does is start the main function in a new thread so it can monitor the source files and restart the thread when they change. Disable this with the use_reloader=False
option.
If you want to be able to run your function when starting the server from a different module, wrap it in a function, and call that function from the other module:
def run_server(dom):
_run_on_start("%s" % dom)
app.run(debug=True, use_reloader=False)
if __name__ == '__main__':
if len(sys.argv) < 2:
raise Exception("Must provide domain for application execution.")
else:
DOM = sys.argv[1]
run_server(DOM)
The "right approach" depends on what you're actually trying to accomplish here. The built-in server is meant for running your application in a local testing environment before deploying it to a production server, so the problem of starting it from a different module doesn't make much sense on its own.
Solution 2
Probably you were looking for Flask.before_first_request
decorator, as in:
@app.before_first_request
def _run_on_start(a_string):
print "doing something important with %s" % a_string
Edwardr
Updated on February 18, 2020Comments
-
Edwardr about 4 years
I'm a little confused about how to do something that I thought would be quite simple. I have a simple app written using
Flask
. It looks something like this:from flask import Flask app = Flask(__name__) def _run_on_start(a_string): print "doing something important with %s" % a_string @app.route('/') def root(): return 'hello world' if __name__ == "__main__": if len(sys.argv) < 2: raise Exception("Must provide domain for application execution.") else: DOM = sys.argv[1] _run_on_start("%s" % DOM) app.run(debug=True)
What I'm finding is that my terminal is outputting the print statements in
_run_on_start
but non of the other usual Flask app debug code. If I remove the call before app.run, the output is normal. Further I'm finding the output of_run_on_start
to be repeated twice on startup, though I don't know if it's some weird output or the function is actually being called twice.I'm assuming this is not the right way to add a function call before you call
app.run
. I looked in the Flask docs and found mentions of various decorators one can use, which allow you to execute a function before/after certain requests but I want to execute the call when the app server is run.Further, I realise that if I call this module from another module, i.e., not when
__name__ != "__main__"
my I won't get my call to_run_on_start
.What's the right approach here? In both cases when I'm starting from the CL and from another module?