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

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

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 models __unicode__ method, specifically the field its returning.

You can prevent this by returning a default value:

def __unicode__(self):
   return self.some_field or uNone

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  # <<<<<<<< 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)  # <<<<<<<< this is OK

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

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.

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