How Can I "override" Deepcopy In Python?

I'd like to override __deepcopy__ for a given SQLAlchemy-mapped class such that it ignores any SQLA attributes but deepcopies everything else that's part of the class. I'm not part

Solution 1:

When (deep-)copying you should not be calling __init__ but instead call __new__.

An example:

def__copy__(self):
    cls = self.__class__
    newobject = cls.__new__(cls)
    newobject.__dict__.update(self.__dict__)
    return newobject

Solution 2:

mavnn is right. For example try change your init of User to:

def__init__(self, user_id = None, name = None):
        self.user_id = user_id
        self.name = name

As for copying mapped instances, I recommend reading this thread

Solution 3:

I'm not an expert on deepcopy, but from the error it looks like you need a parameterless constructor to call self.__class__() without parameters.

Solution 4:

To exclude sqlalchemy columns and mapped attributes you would do something along the lines of:

for attr indir(self):
    ifnot self._sa_class_manager.mapper.has_property(key):
        ...