Handling Exceptions

Which exceptions can be raised?

The types of exceptions that can be raised when calculating affinities are:

exception malaffinity.exceptions.NoAffinityError

Raised when either the shared rated anime between the base user and another user is less than 11, the user does not have any rated anime, or the standard deviation of either users’ scores is zero.

exception malaffinity.exceptions.InvalidUsernameError

Raised when username specified does not exist.

exception malaffinity.exceptions.MALRateLimitExceededError

Raised when MAL’s blocking your request, because you’re going over their rate limit of one request every two seconds. Slow down and try again.

If you’re planning on using this package in an automated or unsupervised script, you’ll want to make sure you account for these getting raised, as not doing so will mean you’ll be bumping into a lot of exceptions, unless you can guarantee none of the above will get raised. For an example snippet of code that can demonstrate this, see Exception Handling Snippet.


exceptions.NoAffinityError and exceptions.InvalidUsernameError are descendants of:

exception malaffinity.exceptions.MALAffinityException

Base class for MALAffinity exceptions.

which means if that base exception gets raised, you know you won’t be able to calculate affinity with that person for some reason, so your script should just move on.

What to do if MALRateLimitExceededError gets raised

exceptions.MALRateLimitExceededError rarely gets raised if you abide by the rate limit of one request every two seconds. If it does get raised, the following should happen:

  • Halt the script for a few seconds. I recommend five.
  • Try again.
  • If you get roadblocked again, just give up. MAL obviously hates you.

Exception Handling Snippet

The above can be demonstrated via something along these lines. Do note that this probably isn’t the best method, but it works.

This should be placed in the section where you are attempting to calculate affinity with another user. Because I wrote this before MALAffinity.comparison() was created, the snippet only shows how you can apply this to calculating affinities, but it can easily be modified, should you wish, to get a comparison of scores.


success = False

for _ in range(2):
        affinity, shared = ma.calculate_affinity("OTHER_USERNAME")

    # Rate limit exceeded. Halt your script and try again
    except malaffinity.exceptions.MALRateLimitExceededError:

    # Any other malaffinity exception.
    # Affinity can't be calculated for some reason.
    # ``MALAffinityException`` is the base exception class for
    # all malaffinity exceptions
    except malaffinity.exceptions.MALAffinityException:

    # Exceptions not covered by malaffinity. Not sure what
    # you could do here. Feel free to handle however you like
    except Exception as e:
        print("Something went wrong. Please contact Xinil for further assistance:")
        print("* https://myanimelist.net/profile/Xinil")
        print("* https://www.reddit.com/user/Xinil")
        print("Please also nag him to create a half-decent MAL API for gods sake.")
        print("Exception: `{}`".format(e))

    # Success!
        success = True

# ``success`` will still be ``False`` if affinity can't been calculated.
# If this is the case, you'll want to stop doing anything with this person
# and move onto the next, so use the statement that will best accomplish this,
# given the layout of your script
if not success:

# Assume from here on that ``affinity`` and ``shared`` hold their corresponding
# values, and feel free to do whatever you want with them

Feel free to use a while loop instead of the above. I’m just a bit wary of them, in case something happens and the script gets stuck in an infinite loop. Your choice.

To see the above snippet in action, visit erkghlerngm44/r-anime-soulmate-finder.