在腌制一个类时，我在python中得到了不同的行为

问题描述

我有以下文件层次结构：

  python / apps / A.py 
 / geometrylib / __ init__。 py 
 /geometrylib/B.py 
 /geometrylib/geometry.py 
 /geometrylib/goemetry.pyx 
 /geometrylib/goemetry.pyd 
  

geometry.pyx和geometry.py包含相同的类Camera（cython版本使用cdef定义类）。 A.py和B.py都导入几何模块。

如果我导入cython版本（编译为geometry.pyd），我可以正确地从B内腌制相机python / geometrylib文件夹中的.py。但是我不能在python / apps文件夹中从A.py中腌制Camera，我得到以下异常：

pickle.PicklingError：不能pickle：它不是找到geometry.Camera

但是，如果我删除了geometry.pyd而我导入python版本（geometry.py），那么我可以从A中腌制相机.py或B.py.除了删除geometry.pyd之外别无其他任何变化，同样的python命令行，在两种情况下都从同一文件夹运行。
为什么会出现这种差异？

挖掘一下我发现C：\Python27 \Lib \中发生异常pickle.py第742行

 尝试：
 __import __（模块）#line 742 
 mod = sys。 modules [module] 
 klass = getattr（mod，name）
除（ImportError，KeyError，AttributeError）：
 raise PicklingError（
不能pickle％r：它不是找到％s。％s％
（obj，模块，名称））
  

在A.py中我导入cython版本（geometry.pyd），（我挑选一个Camera实例来触发预期）模块是几何和 __ import __（模块）触发异常。在A.py中我导入python版本（geometry.py），（我挑选一个Camera实例来触发预期）模块是geometrylib.geometry和 __ import __（模块）正确导入模块。

我已经通过将python / geometrylib添加到PYTHONPATH解决了这个问题，然后我可以使用cython版本从A.py和B.py中正确地腌制相机。

这是怎么回事？我不喜欢我的解决方案。 是否有人有更好的解决方案？

编辑以添加一些额外信息。

另外，根据请求，这是我用来构建cython扩展的setup.py。

 来自distutils.core导入设置来自distutils.extension的
导入扩展
来自Cython.Distutils import build_ext 
 import numpy 
 
 setup（
 cmdclass = {'build_ext'：build_ext}， 
 ext_modules = [Extension（geometry，['geometry.pyx']，include_dirs = [numpy.get_include（），。]）]）
  

解决方案

您正在构建geometry.pyx作为顶级模块，而实际上它是<$ c $的一部分c> geometrylib 包。因此， Camera 类被分配了错误的 __ module __ 值（ geometry 而不是 geometrylib.geometry ）和pickler在尝试查找名为 geometry 的顶级模块时失败。 / p>

您应该遵循标准的包装指南，即将setup.py放入顶级模块（geometrylib）旁边的Python文件夹中。安装调用将如下所示：

  setup（
 cmdclass = {'build_ext'：build_ext}，
 ext_modules = [Extension（geometrylib.geometry，['geometrylib / geometry.pyx']，include_dirs = [numpy.get_include（），。]）]）
  

I have the following file hierarchy:

python/apps/A.py
      /geometrylib/__init__.py
      /geometrylib/B.py
      /geometrylib/geometry.py
      /geometrylib/goemetry.pyx
      /geometrylib/goemetry.pyd

geometry.pyx and geometry.py contain the same class Camera (the cython version defines the class with cdef ). Both A.py and B.py import the geometry module.

If I import the cython version(compiled to geometry.pyd), I can correctly pickle Camera from within B.py in the python/geometrylib folder. But I can't pickle Camera from A.py in the python/apps folder, I get the following exception:

pickle.PicklingError: Can't pickle : it's not found as geometry.Camera

However, if I delete the geometry.pyd and I import the python version(geometry.py) instead, then I can pickle Camera from either A.py or B.py. Nothing else changes apart from deleting geometry.pyd, same python command line, run from the same folder in both cases.why this difference?

Digging a bit I see that the exception occurs in C:\Python27\Lib\pickle.py line 742

try:
    __import__(module)            #line 742
    mod = sys.modules[module]
    klass = getattr(mod, name)
except (ImportError, KeyError, AttributeError):
    raise PicklingError(
        "Can't pickle %r: it's not found as %s.%s" %
        (obj, module, name))

When in A.py I import the cython version(geometry.pyd), (and I pickle a Camera instance to trigger the expection) module is "geometry" and __import__(module) triggers the exception. When in A.py I import the python version(geometry.py),(and I pickle a Camera instance to trigger the expection) module is "geometrylib.geometry" and __import__(module) imports the module correctly.

I have solved the problem by adding python/geometrylib to PYTHONPATH, then I can correctly pickle Camera from both A.py and B.py using the cython version.

Is this how is it supposed to work? I don't like my solution. Does anybody have a better solution?

EDITED to add some extra information.

Also, by request, this is the setup.py I used to build the cython extension.

from distutils.core import setup
from distutils.extension import Extension
from Cython.Distutils import build_ext
import numpy

setup(
    cmdclass = { 'build_ext': build_ext},
    ext_modules = [Extension("geometry", ['geometry.pyx'], include_dirs=[numpy.get_include(), "."])])

解决方案

You are building geometry.pyx as a top-level module, while in fact it is part of geometrylib package. As a result, Camera class gets assigned incorrect __module__ value (geometry instead of geometrylib.geometry) and pickler fails when it tries to find top-level module named geometry.

You should follow standard packaging guidelines, i.e. put setup.py into "Python" folder, next to the top-level module (geometrylib). setup call will look like this:

setup(
    cmdclass = {'build_ext': build_ext},
    ext_modules = [Extension("geometrylib.geometry", ['geometrylib/geometry.pyx'], include_dirs=[numpy.get_include(), "."])])

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