flask-vcoerce.py

# My alternative to `.first_or_404()` that can also handle ValueError's (common use case for me).
# could of course be made to check for more common errors, but for now this has been what I need.

from flask import abort

def vcoerce(validate_p):
    "Sanitises the result of a function from ValueError's and empty results"
    try:
        return validate_p() or abort(404)
    except ValueError:
        abort(400)
    if result is None:
        abort(404)

# Example usage from one of my codebases:
@app.route('/edit/<name>/<sku>')
@restricted
def edit(name, sku):
    return render_template('edit.html',
                           upload=vcoerce(lambda: db.pattern.query.filter_by( # Requires result or 404
                                   sku=snippets.vcoerce(lambda: int(sku))) # Requires parseable as int
                                          .first()),
                           form=Upload())