如何根据时间戳对 InstrumentedList 进行排序？

Question

Currently I have an InstrumentedList that represents a one-to-many relationship in my pyramid app. The relationship is constructed in the following way:

Class project:
 submissions = relationship('Submission', backref='project')

I want to iterate over every submission in a list of projects. However, I want my submissions to be ordered by timestamp (a datetime object)

Here is how I am iterating over my submissions at the moment:

for project in projects:
    for submission in project.submissions:
        # Do some stuff with each submission here

The problem is that the order of my submissions for every project changes whenever the app is reloaded. I need the order to be consistent and ordered by timestamp, how do I go about doing that?

Answer 1

You'll need to specify an ordering in your relationship definition, using the order_by parameter :

class Project(Base):
    # ...
    submissions = relationship('Submission',
        backref='Project', order_by='Submission.timestamp')

Answer 2

@martjin answer is completely ok , but if you want to order your table in descending order , then use desc() function:

class Project(Base):
    # ...
    submissions = relationship('Submission',
        backref='Project', order_by='Submission.timestamp.desc()')