If you have a table with fifty or more fields, you may get tired of repeating them again and again. This shortcut saves typing and also minimizes mismatch errors.

Controller

import pprint
from myapp.model import MyORMClass

class MyController(BaseController):
    def _update_my_attributes(self, my_object):
        data = self.form_result
        log.debug("form input = %s", pprint.pformat(data))
        my_object.field1 = data["field1"]
        ...

        # Or if you prefer to use a loop.
        fieldnames = [x.name for x in MyORMClass.c]
        for fieldname in fieldnames:
            value = data[fieldname]
            setattr(my_object, fieldname, value)


    @validate(schema=SomeSchema(), form="new")
    def create(self):
        my_object = MyORMClass()
        self._update_my_attributes(my_object)
        meta.Session.save(my_object)
        meta.Session.flush()  # Write the object so it has a primary key.
        assert my_object.id, "Failed to add MyORMClass to database."
        meta.Session.commit()
        redirect_to(... display page ...)

    @validate(schema=SomeSchema(), form="edit")
    def update(self):
        my_object = MyORMClass.get(PRIMARY_KEY_THAT_I_KNOW_SOMEHOW)
        self._update_my_attributes(my_object)
        meta.Session.commit()
        redirect_to(... display page ...)

Generic function

If you want to make this even more generic, you can replace ._update_my_attributes with a function:

def update_orm_instance(instance, data):
    """Update a new or existing ORM instance from user input.

    ``instance`` is a SQLAlchemy ORM instance (mapped class).
    ``data`` is a dict of user input whose keys correspond to ``instance`` attributes.
    """
    fieldnames = [x.name for x in instance.__class__.c]
    for fieldname in fieldnames:
        value = data[fieldname]
        setattr(my_object, fieldname, value)

Commentary

Fieldname loops may look convenient but they're kind of magical, and they don't provide any way to customize certain fields; e.g., to convert the value to another type, skip certain fields, set values in related tables, etc. Still, if your needs are straightforward, this might be a pattern for you.

PylonsHQ.

Handling tables with many fields

Controller

Generic function

Commentary

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