cannot catch MySQL IntegrityError in Python

Question

I am using Python/Bottle/SqlAlchemy/MySQL for a web service.

I am trying to catch an IntegrityError raised by calling a stored procedure but I am unable to do that.

Using this

cursor = connection.cursor()
cursor.callproc('my_stored_proc', [arguments])

yields the same result as

try:
    cursor = connection.cursor()
    cursor.callproc('my_stored_proc', [arguments])
except IntegrityError as e:
    print("Error: {}".format(e))
    return {"message": e.message}

I get an IntegrityError exception in both cases. Why is the exception not caught in the latter case?

How / when are you committing your transaction? The IntegrityError will likely be raised when your transaction gets committed, not when calling the stored procedure. — Lukas Graf
– Lukas Graf, Commented Nov 25, 2014 at 20:26

Josh Correia · Accepted Answer · 2021-12-17 02:08:09Z

19

The problem was I was catching the incorrect exception.

It turned out the error raised is actually of type pymysql.err.IntegrityError and not sqlalchemy.exc.IntegrityError as I assumed.

I found out the exception type by doing:

import sys
try:
    cursor = connection.cursor()
    cursor.callproc('my_stored_proc', [arguments])
except:
    print "Unexpected error:", sys.exc_info()[0]

And I saw this printout:

Unexpected error: <class 'pymysql.err.IntegrityError'>

edited Dec 17, 2021 at 2:08

Josh Correia

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answered Nov 25, 2014 at 20:39

Jana

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1 Comment

David Sánchez Over a year ago

just to add since I had a similar problem. I couldnt catch it either. I had to import pymysql; except pymysql.IntegrityError;

Skulas · Accepted Answer · 2020-03-12 16:14:22Z

4

In my case, and also yours, you'd use the sqlalchemy object:

try:
    cursor = connection.cursor()
    cursor.callproc('my_stored_proc', [arguments])
except sqlalchemy.exc.IntegrityError as e:
    print("Error: {}".format(e))
    return {"message": e.message}

answered Mar 12, 2020 at 16:14

Skulas

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Comments

Shaz · Accepted Answer · 2020-06-16 04:07:58Z

2

In my case and may be this helps you too, I was using MYSQL as database so to catch exceptions I need to import exceptions

from django.db.utils import IntegrityError

Then you can try and catch it like this

try:
    #your code
except IntegrityError:
    #your code when integrity error comes

answered Jun 16, 2020 at 4:07

Shaz

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1 Comment

Josh Correia Over a year ago

OP is asking about pymysql, not Django.

Dede95 · Accepted Answer · 2022-08-04 15:41:25Z

0

With pymysql I use:

import pymysql
# some code

try:
   #Your code
except pymysql.err.IntegrityError:
   # Your exception code
except Exception as e:
   # Raise all other exceptions. 
   raise e

answered Aug 4, 2022 at 15:41

Dede95

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