coercing to Unicode need string or buffer NoneType found when rendering in django admin

Question

I have this error since a long time but can t figure it out    Caught TypeError while rendering  coercing to Unicode  need string or buffer  NoneType found  It happens in admin when I try to add or modify on one of my models  display works fine   This is the model   class PS models Model       id ps   models IntegerField null True      client   models ForeignKey Client  null True  blank True      nom du site   models CharField max length 250      rue livraison   models TextField null True      complement adresse   models TextField null True      code postal livraison   models CharField max length 50  null True      ville livraison   models CharField max length 200  null True      pays livraison   models CharField max length 200  null True      distributeur   models CharField max length 50  null True      tarif   models CharField max length 250  null True      type tarif   models CharField max length 50  null True      type installation   models CharField max length 50  null True       def   unicode   self           return self nom du site       property     def pce self                   try              return PCE objects filter ps self  0          except IndexError              return               def get pce self           from pce models import PCE         return PCE objects filter ps self  exclude frequence  6M             def get pce 6m self           from pce models import PCE         return PCE objects filter ps self frequence  6M      Any idea what am i doing wrong here   Traceback       Environment       Request Method  GET     Request URL  http   127 0 0 1 8026 admin ps ps add      Django Version  1 2 5     Python Version  2 7 2     Installed Applications        django contrib auth         django contrib contenttypes         django contrib sessions         django contrib sites         django contrib messages         django contrib admin         easy thumbnails         django extensions         contentadmin         south         sentry         sentry client         indexer         file uploader         paging         pagination         consommation         ps         pce         profil         analytics         document       Installed Middleware        annoying middlewares StaticServe         django middleware common CommonMiddleware         django contrib sessions middleware SessionMiddleware         django middleware csrf CsrfViewMiddleware         django contrib auth middleware AuthenticationMiddleware         django contrib messages middleware MessageMiddleware         pagination middleware PaginationMiddleware         Template error      In template  usr local lib python2 7 dist-packages django contrib admin templates admin includes fieldset html  error at line 19        Caught TypeError while rendering  coercing to Unicode  need string or buffer  NoneType found        9                  for field in line             10                    lt div   if not line fields length is  1     class  field-box   if not field is readonly and field errors    errors   endif       endif    gt           11                          if not line fields length is  1  and not field is readonly      field errors      endif             12                          if field is checkbox             13                              field field      field label tag             14                          else             15                              field label tag             16                              if field is readonly             17                                lt p gt    field contents    lt  p gt           18                              else             19                                   field field              20                              endif             21                          endif             22                          if field field field help text             23                            lt p class  help  gt    field field field help text safe    lt  p gt           24                          endif             25                    lt  div gt           26                  endfor             27            lt  div gt           28          endfor             29    lt  fieldset gt        Traceback      File   usr local lib python2 7 dist-packages django core handlers base py  in get response       100                      response   callback request   callback args    callback kwargs      File   usr local lib python2 7 dist-packages django contrib admin options py  in wrapper       288                  return self admin site admin view view   args    kwargs      File   usr local lib python2 7 dist-packages django utils decorators py  in  wrapped view       76                      response   view func request   args    kwargs      File   usr local lib python2 7 dist-packages django views decorators cache py  in  wrapped view func       78          response   view func request   args    kwargs      File   usr local lib python2 7 dist-packages django contrib admin sites py  in inner       190              return view request   args    kwargs      File   usr local lib python2 7 dist-packages django utils decorators py  in  wrapper       21              return decorator bound func   args    kwargs      File   usr local lib python2 7 dist-packages django utils decorators py  in  wrapped view       76                      response   view func request   args    kwargs      File   usr local lib python2 7 dist-packages django utils decorators py  in bound func       17                  return func self   args2    kwargs2      File   usr local lib python2 7 dist-packages django db transaction py  in  commit on success       299                      res   func  args    kw      File   usr local lib python2 7 dist-packages django contrib admin options py  in add view       909          return self render change form request  context  form url form url  add True      File   usr local lib python2 7 dist-packages django contrib admin options py  in render change form       692             context  context instance context instance      File   usr local lib python2 7 dist-packages django shortcuts   init   py  in render to response       20      return HttpResponse loader render to string  args    kwargs     httpresponse kwargs      File   usr local lib python2 7 dist-packages django template loader py  in render to string       186      return t render context instance      File   usr local lib python2 7 dist-packages django template   init   py  in render       173              return self  render context      File   usr local lib python2 7 dist-packages django template   init   py  in  render       167          return self nodelist render context      File   usr local lib python2 7 dist-packages django template   init   py  in render       796                  bits append self render node node  context       File   usr local lib python2 7 dist-packages django template debug py  in render node       72              result   node render context      File   usr local lib python2 7 dist-packages django template loader tags py  in render       125          return compiled parent  render context      File   usr local lib python2 7 dist-packages django template   init   py  in  render       167          return self nodelist render context      File   usr local lib python2 7 dist-packages django template   init   py  in render       796                  bits append self render node node  context       File   usr local lib python2 7 dist-packages django template debug py  in render node       72              result   node render context      File   usr local lib python2 7 dist-packages django template loader tags py  in render       125          return compiled parent  render context      File   usr local lib python2 7 dist-packages django template   init   py  in  render       167          return self nodelist render context      File   usr local lib python2 7 dist-packages django template   init   py  in render       796                  bits append self render node node  context       File   usr local lib python2 7 dist-packages django template debug py  in render node       72              result   node render context      File   usr local lib python2 7 dist-packages django template loader tags py  in render       62              result   block nodelist render context      File   usr local lib python2 7 dist-packages django template   init   py  in render       796                  bits append self render node node  context       File   usr local lib python2 7 dist-packages django template debug py  in render node       72              result   node render context      File   usr local lib python2 7 dist-packages django template defaulttags py  in render       174                  nodelist append node render context       File   usr local lib python2 7 dist-packages django template loader tags py  in render       139              return self template render context      File   usr local lib python2 7 dist-packages django template   init   py  in render       173              return self  render context      File   usr local lib python2 7 dist-packages django template   init   py  in  render       167          return self nodelist render context      File   usr local lib python2 7 dist-packages django template   init   py  in render       796                  bits append self render node node  context       File   usr local lib python2 7 dist-packages django template debug py  in render node       72              result   node render context      File   usr local lib python2 7 dist-packages django template defaulttags py  in render       174                  nodelist append node render context       File   usr local lib python2 7 dist-packages django template defaulttags py  in render       174                  nodelist append node render context       File   usr local lib python2 7 dist-packages django template defaulttags py  in render       260              return self nodelist false render context      File   usr local lib python2 7 dist-packages django template   init   py  in render       796                  bits append self render node node  context       File   usr local lib python2 7 dist-packages django template debug py  in render node       72              result   node render context      File   usr local lib python2 7 dist-packages django template defaulttags py  in render       260              return self nodelist false render context      File   usr local lib python2 7 dist-packages django template   init   py  in render       796                  bits append self render node node  context       File   usr local lib python2 7 dist-packages django template debug py  in render node       72              result   node render context      File   usr local lib python2 7 dist-packages django template debug py  in render       91              output   force unicode output      File   usr local lib python2 7 dist-packages django utils encoding py  in force unicode       66                  s   unicode s      File   usr local lib python2 7 dist-packages django forms forms py  in   unicode         408          return self as widget       File   usr local lib python2 7 dist-packages django forms forms py  in as widget       450          return widget render name  data  attrs attrs      File   usr local lib python2 7 dist-packages django contrib admin widgets py  in render       247          output    self widget render name  value   args    kwargs       File   usr local lib python2 7 dist-packages django forms widgets py  in render       447          options   self render options choices   value       File   usr local lib python2 7 dist-packages django forms widgets py  in render options       464          for option value  option label in chain self choices  choices       File   usr local lib python2 7 dist-packages django forms models py  in   iter         898                  yield self choice obj      File   usr local lib python2 7 dist-packages django forms models py  in choice       904          return  self field prepare value obj   self field label from instance obj       File   usr local lib python2 7 dist-packages django forms models py  in label from instance       955          return smart unicode obj      File   usr local lib python2 7 dist-packages django utils encoding py  in smart unicode       39      return force unicode s  encoding  strings only  errors      File   usr local lib python2 7 dist-packages django utils encoding py  in force unicode       66                  s   unicode s       Exception Type  TemplateSyntaxError at  admin ps ps add      Exception Value  Caught TypeError while rendering  coercing to Unicode  need string or buffer  NoneType found

User · Accepted Answer

This error happens when you have a   unicode   method that is a returning a field that is not entered  Any blank field is None and Python cannot convert None  so you get the error   In your case  the problem most likely is with the PCE model s   unicode   method  specifically the field its returning   You can prevent this by returning a default value   def   unicode   self      return self some field or u None

User · Answer

Replace the earlier function with the provided one  The simplest solution is   def   unicode   self        return unicode self nom du site

User · Answer

This error might occur when you return an object instead of a string in your   unicode   method  For example   class Author models Model                  name   models CharField        class Book models Model                 author   models ForeignKey Author                     def   unicode   self           return self author     lt  lt  lt  lt  lt  lt  lt  lt  this causes problems   To avoid this error you can cast the author instance to unicode   class Book models Model                  def   unicode   self           return unicode self author      lt  lt  lt  lt  lt  lt  lt  lt  this is OK

User · Answer

In my case it was something else  the object I was saving should first have an id e g  save   should be called  before I could set any kind of relationship with it

User · Answer

First  check that whatever you are returning via unicode is a String    If it is not a string you can change it to a string like this  where self id is an integer   def   unicode   self       return   s    self id   following which  if it still doesn t work  restart your   manage py shell for the changes to take effect and try again  It should work   Best Regards

User · Answer

The return value def   unicode    should be similar to the return value of the related models  tables  for correct viewing of  some field  in django admin panel  You can also use   def   str   self       return self some field

[python] coercing to Unicode: need string or buffer, NoneType found when rendering in django admin

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