I've a Table with the following column:
Column('type', String(128))
How do I set this column to NULL when inserting a new row in database?
I tried doing this:
self.type = NULL;
There is no NULL type in Python so I don't know how to do it.
Instead of trying
self.type = NULL
try as Yaroslav Admin suggested
self.type = None
As Python's equivalent for NULL is None.
null(). Check Ilja Everilä 's answer for more detailsI know this is an old thread but this worked for me
self.type = sqlalchemy.sql.null()
sqlalchemy.null() (v1.2.5)
sqlalchemy.sql.null() - which is treated as SQL NULL - and None which is treated as JSON "null" which is not the same thing.As the other answers have pointed out, an explicit NULL can be inserted by passing None, or in case of SQLAlchemy a null() construct, as the value. In fact PEP-249 "DB-API v2.0" clearly states this in "Type Objects and Constructors":
SQL NULL values are represented by the Python
Nonesingleton on input and output.
As a third option one can simply omit the column, if it is nullable:
t = Table('t', metadata,
Column('a', Integer),
Column('b', Integer))
stmt = t.insert().values(a=1)
engine.execute(stmt)
would effectively insert a new row (1, NULL) in the table t, because a value was not provided for column b. The same applies for mapped classes, which I suppose the original question is actually using (because of the self):
class T(Base):
__tablename__ = 't'
id = Column(Integer, primary_key=True)
a = Column(Integer)
b = Column(Integer)
session.add(T(a=1))
session.commit()
again effectively results in (default, 1, NULL) being inserted.
You can declare:
Column('type', String(128), default=None)
