How To Convert Python Object Into String?

QuerySelectField is displaying the query correctly but its not saving in the database, it shows the following error while submitting. ProgrammingError: (ProgrammingError) can't ada

Solution 1:

Your problem lies here:

form.populate_obj(article)

This basically assigns the form field values to the database object's corresponding fields. However, you are not using a SQLAlchemy relationship (you should!) so article.category needs to contain the name (why not ID?!) of the category. However, the QuerySelectField has the database object (i.e. a Category instance) as its value.

You have three options; the third one is the preferred one:

• Use a normal SelectField with choices populated from the database

• Don't use populate_obj but assign the category manually using

  article.category = form.category.data.name
  

• Rename the category column in Article to e.g. category_name and use a relationship() so Article.category does not contain the name but a Category object.

Solution 2:

The category relationship in your Article model is not correct. It has two problems:

1. you have not provided the data type for the column.
2. Article.category needs to be a relationship, not a column.

If you modify your Article class to something like this things should improve:

class Article(Base):
    ...
    category_name = Column(String(100), ForeignKey(Category.name), nullable=False)
    category = relationship(Category)

If you do that SQLAlchemy will know that the category property must be a Category instance and will automatically load and save Category instances as needed.

Solution 3:

Add Relationship to your Model Fields.