第三方包集成问题¶
Third Party Integration Issues
我收到与 “numpy.int64”、 “numpy.bool_” 等相关的错误。¶
I’m getting errors related to “numpy.int64”, “numpy.bool_”, etc.
numpy 包拥有一套扩展自 Python 数值类型的专有数值数据类型，但这些类型在某些情况下表现出的行为可能与 SQLAlchemy 的行为不兼容，有时甚至无法与所使用的底层 DBAPI 驱动兼容。
可能出现的两类典型错误包括：
ProgrammingError: can't adapt type 'numpy.int64'（在 psycopg2 等后端中出现）；ArgumentError: SQL expression object expected, got object of type <class 'numpy.bool_'> instead；
在较新版本的 SQLAlchemy 中，后者的报错信息可能为：
ArgumentError: SQL expression for WHERE/HAVING role expected, got True。
第一类错误的原因在于 psycopg2 等驱动缺少对 int64 类型的适配支持——这种类型不能直接作为参数传入查询中。例如下面的代码会触发该问题：
import numpy
class A(Base):
__tablename__ = "a"
id = Column(Integer, primary_key=True)
data = Column(Integer)
# .. 稍后
session.add(A(data=numpy.int64(10)))
session.commit()第二类错误则是因为 numpy.int64 类型重写了其 __eq__() 方法，并强制返回 numpy.True 或 numpy.False，这会破坏 SQLAlchemy 表达式语言的行为。SQLAlchemy 期望从 Python 的等值比较中返回 ColumnElement 类型的表达式：
>>> import numpy
>>> from sqlalchemy import column, Integer
>>> print(column("x", Integer) == numpy.int64(10)) # 正常
x = :x_1
>>> print(numpy.int64(10) == column("x", Integer)) # 出错
False上述两类问题的解决方式是一样的：应将特殊的 numpy 数据类型转换为标准 Python 值。常见的转换方式包括对 numpy.int32 和 numpy.int64 使用 Python 内建的 int() 函数，对 numpy.float32 使用 float() 函数：
data = numpy.int64(10)
session.add(A(data=int(data)))
result = session.execute(select(A.data).where(int(data) == A.data))
session.commit()The numpy package has its own numeric datatypes that extend from Python’s numeric types, but contain some behaviors that in some cases make them impossible to reconcile with some of SQLAlchemy’s behaviors, as well as in some cases with those of the underlying DBAPI driver in use.
Two errors which can occur are ProgrammingError: can't adapt type 'numpy.int64'
on a backend such as psycopg2, and ArgumentError: SQL expression object
expected, got object of type <class 'numpy.bool_'> instead; in
more recent versions of SQLAlchemy this may be ArgumentError: SQL expression
for WHERE/HAVING role expected, got True.
In the first case, the issue is due to psycopg2 not having an appropriate
lookup entry for the int64 datatype such that it is not accepted directly
by queries. This may be illustrated from code based on the following:
import numpy
class A(Base):
__tablename__ = "a"
id = Column(Integer, primary_key=True)
data = Column(Integer)
# .. later
session.add(A(data=numpy.int64(10)))
session.commit()In the latter case, the issue is due to the numpy.int64 datatype overriding
the __eq__() method and enforcing that the return type of an expression is
numpy.True or numpy.False, which breaks SQLAlchemy’s expression
language behavior that expects to return ColumnElement
expressions from Python equality comparisons:
>>> import numpy
>>> from sqlalchemy import column, Integer
>>> print(column("x", Integer) == numpy.int64(10)) # works
x = :x_1
>>> print(numpy.int64(10) == column("x", Integer)) # breaks
FalseThese errors are both solved in the same way, which is that special numpy
datatypes need to be replaced with regular Python values. Examples include
applying the Python int() function to types like numpy.int32 and
numpy.int64 and the Python float() function to numpy.float32:
data = numpy.int64(10)
session.add(A(data=int(data)))
result = session.execute(select(A.data).where(int(data) == A.data))
session.commit()预期 WHERE/HAVING 角色的 SQL 表达式为 True¶
SQL expression for WHERE/HAVING role expected, got True