Python Django - delaying ValidationError until for loop completes

Question

I'm working on an app that simulates a social media site. I currently have a form where users can enter in their friends' emails so they can be invited to join the app.

Let's say we have a user who enters in three email addresses to the email form which are then saved as a list of strings:

emails_to_invite = ["[email protected]", "[email protected]", "[email protected]"]

In the database, we already have a list of users who have already been invited to the site:

current_users = ["[email protected]", "[email protected]", "[email protected]", "[email protected]"]

So we have two users who have already been invited: [email protected] and [email protected].

I'm trying to write some code that returns a ValidationError and can list both matched users in the message. Here's what I have so far:

for email in emails_to_invite:
 if email in current_users:
  raise forms.ValidationError(f"{email} is already in the database.")

Here's how I want this error to display:

[email protected] is already in the database.
[email protected] is already in the database.

But right now, the error only displays the first email:

[email protected] is already in the database.

I also need [email protected] to display too. It appears that the for loop stops once it recognizes one match, but I need it to keep going until it recognizes all matches. Can anyone offer some suggestions?

Adam Smooch · Accepted Answer · 2022-11-16 21:43:57Z

1

If you don't want an Exception in a code-block to halt your execution (and hide further exceptions, as you've found), put the susceptible code in a a try/except block to handle the error as you see fit.

To later raise the exception, consider using something like:

raised_exceptions = []
<loop that might raise exceptions>
  try:
    <loop that might raise exceptions>
  except Exception as e:
    raised_exceptions.append(e)

<do something with the exceptions you saved>

That being said, IMO you shouldn't be using exceptions in this way - consider returning a series of lists, one per possible outcome, instead: email sent and already invited (and/or joined user)

answered Nov 16, 2022 at 21:43

Adam Smooch

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