Question

我有一个奇怪的问题，SQLAlchemy很少发生。

我有两个映射类：

class BinaryTree:
"""
A Binary Tree, i.e. arity 2.

=== Attributes ===
@param object data: data for this binary tree node
@param BinaryTree|None left: left child of this binary tree node
@param BinaryTree|None right: right child of this binary tree node
"""

def __init__(self, data, left=None, right=None):
    """
    Create BinaryTree self with data and children left and right.

    @param BinaryTree self: this binary tree
    @param object data: data of this node
    @param BinaryTree|None left: left child
    @param BinaryTree|None right: right child
    @rtype: None
    """
    self.data, self.left, self.right = data, left, right

def __eq__(self, other):
    """
    Return whether BinaryTree self is equivalent to other.

    @param BinaryTree self: this binary tree
    @param Any other: object to check equivalence to self
    @rtype: bool

    >>> BinaryTree(7).__eq__("seven")
    False
    >>> b1 = BinaryTree(7, BinaryTree(5))
    >>> b1.__eq__(BinaryTree(7, BinaryTree(5), None))
    True
    """
    return (type(self) == type(other) and
            self.data == other.data and
            (self.left, self.right) == (other.left, other.right))

def __repr__(self):
    """
    Represent BinaryTree (self) as a string that can be evaluated to
    produce an equivalent BinaryTree.

    @param BinaryTree self: this binary tree
    @rtype: str

    >>> BinaryTree(1, BinaryTree(2), BinaryTree(3))
    BinaryTree(1, BinaryTree(2, None, None), BinaryTree(3, None, None))
    """
    return "BinaryTree({}, {}, {})".format(repr(self.data),
                                           repr(self.left),
                                           repr(self.right))

def __str__(self, indent=""):
    """
    Return a user-friendly string representing BinaryTree (self)
    inorder.  Indent by indent.

    >>> b = BinaryTree(1, BinaryTree(2, BinaryTree(3)), BinaryTree(4))
    >>> print(b)
        4
    1
        2
            3
    <BLANKLINE>
    """
    right_tree = (self.right.__str__(
        indent + "    ") if self.right else "")
    left_tree = self.left.__str__(indent + "    ") if self.left else ""
    return (right_tree + "{}{}\n".format(indent, str(self.data)) +
            left_tree)

def __contains__(self, value):
    """
    Return whether tree rooted at node contains value.

    @param BinaryTree self: binary tree to search for value
    @param object value: value to search for
    @rtype: bool

    >>> BinaryTree(5, BinaryTree(7), BinaryTree(9)).__contains__(7)
    True
    """
    return (self.data == value or
            (self.left and value in self.left) or
            (self.right and value in self.right))

def list_longest_path(node):
"""
List the data in a longest path of node.

@param BinaryTree|None node: tree to list longest path of
@rtype: list[object]

>>> list_longest_path(None)
[]
>>> list_longest_path(BinaryTree(5))
[5]
>>> b1 = BinaryTree(7)
>>> b2 = BinaryTree(3, BinaryTree(2), None)
>>> b3 = BinaryTree(5, b2, b1)
>>> list_longest_path(b3)
[5, 3, 2]
"""
if node is None:
    return []
elif not node.left and not node.right:
    return [node]
else:
    return [node]+list_longest_path(node.left)+list_longest_path(node.right)

在我的应用程序中，我执行以下操作：

class cQuantum(Base):
    __tablename__ = 'mesQuantum'
    quanID = Column(UNIQUEIDENTIFIER, primary_key=True, autoincrement=False)
    quantityTransferred = Column(Float)
    quantityActual = Column(Float)
    received = Column(DateTime)

class cTransfer(Base):
    __tablename__ = 'mesTransfer'
    transferID = Column(UNIQUEIDENTIFIER, primary_key=True, autoincrement=False)
    quanID = Column(UNIQUEIDENTIFIER, ForeignKey('mesQuantum.quanID'))
    quantityTransferred = Column(Float)
    quantityActual = Column(Float)
    finished = Column(DateTime)
    quanObj = relationship('cQuantum', foreign_keys=[quanID], lazy='joined')

在99％的情况下一切正常。

但有时只更新cQuantum和cTransfer中的quantityTransferred列，其余的（quantityActual，finished和received）保持None（数据库中为NULL，默认值）。值和值2都不是无。

对我来说特别困惑的是声明是如何可能的

try:
    session = saSession()
    trans = session.query(cTransfer).filter(#some expression).first()
    trans.finished = value
    trans.quantityTransferred = trans.quantityActual = value2
    trans.quanObj.quantityTransferred = trans.quanObj.quantityActual = value2
    trans.quanObj.received = value
    session.commit()
except Exception as e:
    session.rollback()
finally:
    session.close()

绑定到单个会话的两个对象在提交时会在数据库中产生不同的结果吗？

抱歉这个冗长的问题。不知道如何用更少的线条来解释它。：）

在SQLAlchemy中链分配列

0 个答案: