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POFlask-SQLAlchemy: How to conditionally insert or update a row
 

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  1. POFlask-SQLAlchemy: How to conditionally insert or update a row
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    <p>My application uses a combination of Flask, Flask-SQLAlchemy, Flask-WTF and Jinja2.</p> <p>In its current incarnation, I have a settings table. The table will only have one record with one field. Initially the table contains zero records. </p> <p>What I want to achieve is:</p> <ul> <li>Given that no entries exist in db, then show empty form ready for user input</li> <li>Given that an entry exist, show the entry, and</li> <li>if the user changes the value, then update the rec in db.</li> </ul> <p>Here is my code:</p> <p><strong>models.py</strong></p> <pre><code>class Provider(db.Model): id = db.Column(db.Integer, primary_key = True) rssfeed = db.Column(db.String(120), unique = True) def __init__(self, rssfeed): self.rssfeed = rssfeed def __repr__(self): return '&lt;NZBMatrix feed url %r&gt;' % self.rssfeed </code></pre> <p><strong>forms.py</strong></p> <pre><code>class SettingsForm(Form): rssfeed = TextField('rssfed', validators= [Required()]) </code></pre> <p><strong>views.py</strong></p> <pre><code> @app.route('/settings', methods=["GET","POST"]) def settings(): """ show settings """ provider = Provider.query.get(1) form = SettingsForm(obj=provider) print provider if request.method == "POST" and form.validate(): if Provider.query.get(1) is None: provider = Provider(rssfeed=form.rssfeed.data) form.populate_obj(provider) db.session.add(provider) db.session.commit() flash("Settings added") return render_template("settings.html", form=form) </code></pre> <p>As it stands this code creates a record if it doesn't exists but the <code>rssfeed</code> column is empty. </p> <p>How can I change this code so that it will <code>INSERT</code> if the record doesn't exist and <code>UPDATE</code> if it does?</p>
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    1. UShappygoat
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    1. COJust FYI - `form.validate` should be `form.validate()` - a function is always truthy, but your form *might* not pass validation.
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      1. USSean Vieira
    2. COThanks for pointing that out!
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