Temporarily Drop a Foreign Key Constraint, Python, SQLAlchemy

TempDropFKContraint.py

class TempDropConstraint(object):
  
  def __init__(self, table, column):
    self.table = table
    self.table_name = table.__tablename__
    self.column = column
    self.constraint = list(self.table.__table__.columns[column.name].foreign_keys)[0]
    self.constraint_name = self.constraint.name
    self.referred_table = self.constraint.column.table.name
    self.referred_columns = self.constraint.column.name
  
  def __enter__(self):
    sql = """
      ALTER TABLE {table}
      DROP CONSTRAINT {constraint}
    """.format(
      table=self.table_name,
      constraint=self.constraint_name
    )
    db.session.execute(sql)
    log.info('Dropped constraint')
  
  def __exit__(self, exc_type, exc_val, exc_tb):
  
    sql = """
      ALTER TABLE {table_name}
      ADD CONSTRAINT {constraint_name}
      FOREIGN KEY ({column})
      REFERENCES {referred_table} ({referred_columns})
    """.format(
      table_name=self.table_name,
      constraint_name=self.constraint_name,
      column=self.column.name,
      referred_table=self.referred_table,
      referred_columns=self.referred_columns
    )
    
    db.session.execute(sql)
    log.info('Added constraint')
  
with TempDropConstraint(Entity, Entity.column):
  # Thing which doesn't need FK constraint