Question

I consider it bad style to use try: except: for flow control, but I can’t figure out how to write the following code to test if a DB field in Django exists. This is the “dirty” code which works:

@receiver(pre_save, sender=UserProfile)
def create_user_profile(sender, instance=None, **kwargs):

    try:
        print str(instance.bank_account)
    except:
        print 'No account'

I would rather wanna do something like this, but I get an exception when the if statement is run and the object does not exist:

@receiver(pre_save, sender=UserProfile)
def create_user_profile(sender, instance=None, **kwargs):

    if instance.bank_account is None:
        print 'No account'
    else:
        print str(instance.bank_account)

Answer 1

I’m guessing you encounter a BankAccount.DoesNotExist error? If that’s the case, you could reverse the relationship between UserProfile and BankAccount. Have a look at Django ticket #10227 to find out what’s going on here.

That being said, if I needed to work with your code I’d rather see an explicit try...except instead of a workaround, unless that workaround actually makes sense.