Fastest way to get the first object from a queryset in django

Question

Often I find myself wanting to get the first object from a queryset in Django  or return None if there aren t any   There are lots of ways to do this which all work   But I m wondering which is the most performant   qs   MyModel objects filter blah   blah  if qs count    gt  0      return qs 0  else      return None   Does this result in two database calls   That seems wasteful   Is this any faster    qs   MyModel objects filter blah   blah  if len qs   gt  0      return qs 0  else      return None   Another option would be   qs   MyModel objects filter blah   blah  try      return qs 0  except IndexError      return None   This generates a single database call  which is good   But requires creating an exception object a lot of the time  which is a very memory-intensive thing to do when all you really need is a trivial if-test   How can I do this with just a single database call and without churning memory with exception objects

User · Answer

It can be like this  obj   model objects filter id emp id  0    or  obj   model objects latest  id

User · Answer

This could work as well   def get first element MyModel       my query   MyModel objects all       return my query  1    if it s empty  then returns an empty list  otherwise it returns the first element inside a list

User · Answer

Now  in Django 1 9 you have first    method for querysets   YourModel objects all   first     This is a better way than  get   or  0  because it does not throw an exception if queryset is empty  Therafore  you don t need to check using exists

User · Answer

You can use array slicing  Entry objects all    1  get    Which can be used with  filter    Entry objects filter    1  get    You wouldn t want to first turn it into a list because that would force a full database call of all the records  Just do the above and it will only pull the first  You could even use  order by   to ensure you get the first you want  Be sure to add the  get   or else you will get a QuerySet back and not an object

User · Answer

If you plan to get first element often - you can extend QuerySet in this direction    class FirstQuerySet models query QuerySet       def first self           return self 0    class ManagerWithFirstQuery models Manager       def get query set self           return FirstQuerySet self model    Define model like this    class MyModel models Model       objects   ManagerWithFirstQuery     And use it like this    first object   MyModel objects filter x 100  first

User · Answer

Use the convenience methods  first   and  last    MyModel objects filter blah blah  first    They both swallow the resulting exception and return None if the queryset returns no objects  These were added in Django 1 6  which was released in Nov 2013

User · Answer

You should use django methods  like exists  Its there for you to use it   if qs exists        return qs 0  return None

User · Answer

r   list qs  1   if r    return r 0  return None

[python] Fastest way to get the first object from a queryset in django?

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