CODEWITHSUNDEEP
pythonsqlalchemyflask
Chris McKinnel
Chris McKinnel

Reputation: 15082

Can't catch _mysql_exceptions.OperationalError in Flask app

I have a Flask app with a route that looks like this:

from _mysql_exceptions import OperationalError

@mod.route('/', methods=['POST'])
def do_something_route():
    try:
        do_something(request.form)
    except OperationalError:
        message = {"error": "something went wrong"}
        return jsonify(message, mimetype='application/json'), 400

The do_something() function:

def do_something(self, form_data):
    model = MyModel()
    for key in form_data:
        if hasattr(model, key):
            setattr(model, key, form_data.get(key))
    db.session.add(model)
    db.session.commit()
    return model

When I send garbage data to do_something_route that violates my DB constraints, an OperationalError exception is raised and a response with a status code of 500 and the stack trace is returned, not my jsonified message with a status of 400.

When I try this is a plain old python shell, it seems to work as expected:

>>> from _mysql_exceptions import OperationalError
>>> raise OperationalError
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
_mysql_exceptions.OperationalError

>>> try:
...     raise OperationalError
... except OperationalError:
...     print 'test'
...
test

Why is except OperationalError: not catching OperationalError exceptions? Is Flask doing some black magic that is returning a response early?

Upvotes: 2

Views: 5551

Answers (1)

buxizhizhoum
buxizhizhoum

Reputation: 1929

from  sqlalchemy.exc import OperationalError
try:
     # do something
except OperationalError:
     # do something

Upvotes: 2

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