Good ways to sort a queryset - Django

Question

what I m trying to do is this    get the 30 Authors with highest score   Author objects order by  -score    30    order the authors by last name     Any suggestions

User · Answer

Here s a way that allows for ties for the cut-off score   author count   Author objects count   cut off score   Author objects order by  -score   values list  score   min 30  author count   top authors   Author objects filter score  gte cut off score  order by  last name     You may get more than 30 authors in top authors this way and the min 30 author count  is there incase you have fewer than 30 authors

User · Answer

What about  import operator  auths   Author objects order by  -score    30  ordered   sorted auths  key operator attrgetter  last name      In Django 1 4 and newer you can order by providing multiple fields  Reference  https   docs djangoproject com en dev ref models querysets  order-by  order by  fields   By default  results returned by a QuerySet are ordered by the ordering tuple given by the ordering option in the model   s Meta  You can override this on a per-QuerySet basis by using the order by method   Example   ordered authors   Author objects order by  -score    last name    30    The result above will be ordered by score descending  then by last name ascending  The negative sign in front of  -score  indicates descending order  Ascending order is implied

User · Answer

I just wanted to illustrate that the built-in solutions  SQL-only  are not always the best ones   At first I thought that because Django s QuerySet objects order by method accepts multiple arguments  you could easily chain them   ordered authors   Author objects order by  -score    last name    30    But  it does not work as you would expect   Case in point  first is a list of presidents sorted by score  selecting top 5 for easier reading     gt  gt  gt  auths   Author objects order by  -score    5   gt  gt  gt  for x in auths  print x      James Monroe  487  Ulysses Simpson  474  Harry Truman  471  Benjamin Harrison  467  Gerald Rudolph  464    Using Alex Martelli s solution which accurately provides the top 5 people sorted by last name    gt  gt  gt  for x in sorted auths  key operator attrgetter  last name     print x      Benjamin Harrison  467  James Monroe  487  Gerald Rudolph  464  Ulysses Simpson  474  Harry Truman  471    And now the combined order by call    gt  gt  gt  myauths   Author objects order by  -score    last name    5   gt  gt  gt  for x in myauths  print x      James Monroe  487  Ulysses Simpson  474  Harry Truman  471  Benjamin Harrison  467  Gerald Rudolph  464    As you can see it is the same result as the first one  meaning it doesn t work as you would expect

[python] Good ways to sort a queryset? - Django

Examples related to python

Examples related to django

Examples related to django-models