I have a function now to find a model instance based on matching the string which the model returns. This is obviously not efficient. I was wondering if Django has a method to find a model instance based only on the string rather than by filtering by the instance attributes.
def parse_book(book_name):
for book in Book.objects.all():
if str(book) == book_name:
return book
No, there is no way to do that more efficiently; you can either search using the database, in which case you need to search the fields in the model, or you can search the returned rows using Python, like you are doing.
(One way around this that some people use is /denormalization/ -- essentially saving the string with the model itself in the database, and then using it as an index.)
However, your string almost certainly has some relation to the fields that are in the model -- ideally, it is entirely determined by them. If that is true, then you can parse the string that you get to determine what the fields should be, and then do a lookup in the database based on those values.
Example code:
class Book(models.Model):
title = models.CharField(max_length=200)
author = models.CharField(max_length=200)
def __str__(self):
return self.title + ": " + self.author
def parse_book(book_name):
title, author = book_name.split(": ", 1)
try:
return Book.objects.get(title=title, author=author)
except Book.DoesNotExist:
return None
Book.objects.get(name=book_name)orBook.objects.filter(book=book_name)?