Posting a python dictionary as an entered field on a form

Question

I am writing an application which will allow users to set up python scripts to run at set intervals. I am using APSCheduler combined with SQLAlchemy as a data source and Flask for my web UI.

I have a screen with the following markup for setting up jobs:

<form method="POST">
    <input type="text" name="JobDesc">
    <input type="text" name="function">
    <input type="text" name="args">
    <input type="text" name="kwargs">
    <select name="trigger">
        <option value="interval" selected>Interval</option> <!--Adding other job types later-->
    </select>
    <input type="number" name="minutes">
    <select name="coalesce">
        <option value=1>True</option>
        <option value=0 selected>False</option>
    </select>
    <input type="submit">
</form>

This forms "submit" button triggers the below script, to add the record to the database

@app.route('/addjob', methods=['GET', 'POST'])
def JobConfig():
    if flask.request.method == 'POST':

        if flask.request.form['args'] == '': # '' == None returns False. :(
            args = None
        else:
            args = flask.request.form['args']

        if flask.request.form['kwargs'] == '':
            kwargs = None
        else:
            print(flask.request.form['kwargs'])
            kwargs = flask.request.form['kwargs']

        scheduler.add_job(
            trigger=str(flask.request.form['trigger']),
            func=str(flask.request.form['function']),
            minutes=int(flask.request.form['minutes']),
            coalesce=bool(flask.request.form['coalesce']),
            args=args,
            kwargs=kwargs,
            name=str(flask.request.form['JobDesc']),
        )

        return 'Success', 201
    elif flask.request.method == 'GET':
        return flask.render_template('JobEntry.html')
    else:
        return flask.abort(400)

APScheduler has a number of key fields:

• Function: Details of the function to be scheduled (for example: JOBS.TestJob:Test runs the Test function in the the Testjob.py file in the JOBS folder).
• args: List of functions to supply to the function.
• kwargs: Dictionary of functions to supply to the function.

Unfortunately, while the entry screen works fine when args and kwargs are blank, if you try to entry any arguments I get an error. For example, if I the Test function is expecting an argument "Abbrev" and I enter {"Abbrev":"Test1"} into the kwargs field:

File "C:\Python34\lib\site-packages\apscheduler\schedulers\base.py", line 334, in add_job
'kwargs': dict(kwargs) if kwargs is not None else {},
ValueError: dictionary update sequence element #0 has length 1; 2 is required

Would anyone be able to point me in the right direction? I'm not sure if this is an error in my python of if I need to use something other than vanilla HTTP POST requests (JSON?) to send the data.

Answer 1

This would indeed work better with JSON input. As the error implies, you need to give a dict as the "kwargs" argument and a tuple or list as the "args" argument. Alternatively you can parse the kwargs into a dict yourself, however you wish.