同一命名空间中的包：无法在安装脚本中导入模块

Question

我很好奇下面的情况。假设我有两个名为 project_alpha 和 project_bravo 的项目，它们都定义了一个顶级命名空间包 mymeta。布局：

project_alpha/
   -> mymeta/
        -> __init__.py
        -> project_alpha/
             -> __init__.py
             -> version.py
   -> setup.py

project_bravo/
   -> mymeta/
        -> __init__.py
        -> project_bravo/
             -> __init__.py
             -> version.py
   -> setup.py

两个 mymeta/__init__.py 都只包含行 __import__('pkg_resources').declare_namespace(__name__)（根据 namespace section in setuptools docs）。两个 version.py 的内容：

__version_info__ = (0, 9, 9, 'dev0')
__version__ = '.'.join((str(entry) for entry in __version_info__))

project_alpha 的 setup.py 脚本非常简单。声明命名空间包mymeta，版本取自version模块：

# project_alpha
from setuptools import find_packages, setup
from mymeta.project_alpha.version import __version__

setup(
    name='mymeta.project-alpha',
    version=__version__,
    namespace_packages=['mymeta'],
    packages=find_packages(),
)

project_bravo 的 setup.py 脚本具有相同的结构，但有一点不同：project_bravo 在构建时依赖于 project_alpha：

from setuptools import find_packages, setup
from mymeta.project_bravo.version import __version__

setup(
    name='mymeta.project-bravo',
    version=__version__,
    namespace_packages=['mymeta'],
    setup_requires=['mymeta.project-alpha'],
    packages=find_packages(),
)

构建 project_bravo 时，出现以下错误：

~/project_bravo $ python setup.py sdist 
Traceback (most recent call last):
  File "/tmp/tstenv/lib/python3.5/site-packages/setuptools/sandbox.py", line 156, in save_modules
    yield saved
  File "/tmp/tstenv/lib/python3.5/site-packages/setuptools/sandbox.py", line 197, in setup_context
    yield
  File "/tmp/tstenv/lib/python3.5/site-packages/setuptools/sandbox.py", line 246, in run_setup
    DirectorySandbox(setup_dir).run(runner)
  File "/tmp/tstenv/lib/python3.5/site-packages/setuptools/sandbox.py", line 276, in run
    return func()
  File "/tmp/tstenv/lib/python3.5/site-packages/setuptools/sandbox.py", line 245, in runner
    _execfile(setup_script, ns)
  File "/tmp/tstenv/lib/python3.5/site-packages/setuptools/sandbox.py", line 47, in _execfile
    exec(code, globals, locals)
  File "/tmp/easy_install-ahmxos98/mymeta.project-alpha-0.9.9.dev0/setup.py", line 6, in <module>
    try:
ImportError: No module named 'mymeta.project_alpha'

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "setup.py", line 22, in <module>
    packages=find_packages(),
  File "/usr/lib64/python3.5/distutils/core.py", line 108, in setup
    _setup_distribution = dist = klass(attrs)
  File "/tmp/tstenv/lib/python3.5/site-packages/setuptools/dist.py", line 315, in __init__
    self.fetch_build_eggs(attrs['setup_requires'])
  File "/tmp/tstenv/lib/python3.5/site-packages/setuptools/dist.py", line 361, in fetch_build_eggs
    replace_conflicting=True,
  File "/tmp/tstenv/lib/python3.5/site-packages/pkg_resources/__init__.py", line 853, in resolve
    dist = best[req.key] = env.best_match(req, ws, installer)
  File "/tmp/tstenv/lib/python3.5/site-packages/pkg_resources/__init__.py", line 1125, in best_match
    return self.obtain(req, installer)
  File "/tmp/tstenv/lib/python3.5/site-packages/pkg_resources/__init__.py", line 1137, in obtain
    return installer(requirement)
  File "/tmp/tstenv/lib/python3.5/site-packages/setuptools/dist.py", line 429, in fetch_build_egg
    return cmd.easy_install(req)
  File "/tmp/tstenv/lib/python3.5/site-packages/setuptools/command/easy_install.py", line 665, in easy_install
    return self.install_item(spec, dist.location, tmpdir, deps)
  File "/tmp/tstenv/lib/python3.5/site-packages/setuptools/command/easy_install.py", line 695, in install_item
    dists = self.install_eggs(spec, download, tmpdir)
  File "/tmp/tstenv/lib/python3.5/site-packages/setuptools/command/easy_install.py", line 876, in install_eggs
    return self.build_and_install(setup_script, setup_base)
  File "/tmp/tstenv/lib/python3.5/site-packages/setuptools/command/easy_install.py", line 1115, in build_and_install
    self.run_setup(setup_script, setup_base, args)
  File "/tmp/tstenv/lib/python3.5/site-packages/setuptools/command/easy_install.py", line 1101, in run_setup
    run_setup(setup_script, args)
  File "/tmp/tstenv/lib/python3.5/site-packages/setuptools/sandbox.py", line 249, in run_setup
    raise
  File "/usr/lib64/python3.5/contextlib.py", line 77, in __exit__
    self.gen.throw(type, value, traceback)
  File "/tmp/tstenv/lib/python3.5/site-packages/setuptools/sandbox.py", line 197, in setup_context
    yield
  File "/usr/lib64/python3.5/contextlib.py", line 77, in __exit__
    self.gen.throw(type, value, traceback)
  File "/tmp/tstenv/lib/python3.5/site-packages/setuptools/sandbox.py", line 168, in save_modules
    saved_exc.resume()
  File "/tmp/tstenv/lib/python3.5/site-packages/setuptools/sandbox.py", line 143, in resume
    six.reraise(type, exc, self._tb)
  File "/tmp/tstenv/lib/python3.5/site-packages/pkg_resources/_vendor/six.py", line 685, in reraise
    raise value.with_traceback(tb)
  File "/tmp/tstenv/lib/python3.5/site-packages/setuptools/sandbox.py", line 156, in save_modules
    yield saved
  File "/tmp/tstenv/lib/python3.5/site-packages/setuptools/sandbox.py", line 197, in setup_context
    yield
  File "/tmp/tstenv/lib/python3.5/site-packages/setuptools/sandbox.py", line 246, in run_setup
    DirectorySandbox(setup_dir).run(runner)
  File "/tmp/tstenv/lib/python3.5/site-packages/setuptools/sandbox.py", line 276, in run
    return func()
  File "/tmp/tstenv/lib/python3.5/site-packages/setuptools/sandbox.py", line 245, in runner
    _execfile(setup_script, ns)
  File "/tmp/tstenv/lib/python3.5/site-packages/setuptools/sandbox.py", line 47, in _execfile
    exec(code, globals, locals)
  File "/tmp/easy_install-ahmxos98/mymeta.project-alpha-0.9.9.dev0/setup.py", line 6, in <module>
    try:
ImportError: No module named 'mymeta.project_alpha'

很遗憾，我不明白这里的错误。跟进口订单有关系吧？如果我在 project_bravo/setup.py 中注释掉 mymeta.project_bravo.version 的导入并将 version 替换为一些硬编码字符串，突然构建成功...

编辑：我介绍了这个问题的解决方法。我没有尝试直接导入版本，而是 exec 版本模块以避免导入问题。当然，这不是一个合适的解决方案，因此不会将其作为答案发布，但仍然在这里：

__version__ = None # if the exec fails, leave the version unset, the resulting build version will be 0.0.0
version_script_path = os.path.relpath(os.path.join(os.path.dirname(__file__), 'mymeta', 'project_alpha', 'version.py'))
with open(version_script_path) as version_script:
    exec(version_script.read())

读取并执行版本脚本后，版本被初始化，因此不需要从mymeta包中导入任何东西。

Answer 1

如评论中所述：命令

$ python setup.py sdist

for mymeta.project_bravo 从私有 pypi 存储库下载 mymeta.project_alpha 的 egg。

命名空间包的导入非常微妙。

例如我发现当我在我的环境中定期安装 ns.a 和 ns.b 并在 site-packages 目录的 .pth 文件中提供 ns.d 的导入路径时，它不会工作，无论。但是，当我符号链接到 site-packeges/ns 目录中的 ns.d 时，它将起作用。

如果我安装 none 个组件并在 site-packages 目录的 .pth 中提供所有路径，一切正常。

如果我定期安装所有组件，一切正常。

就在我混概念的时候不行。

因此我怀疑这也可能是这里的问题：导入路径的不同策略。

您可能想尝试将 __init__.py 文件修改为：

from pkgutil import extend_path

__path__ = extend_path(__path__, __name__)
__import__('pkg_resources').declare_namespace(__name__)

我对我做命名空间包的决定感到遗憾。我再也不会这样做了。

Answer 2

差不多一年后，我再次遇到这个问题，python>=3.3 的解决方案是使用 PEP 420 中指定的隐式命名空间包。项目结构几乎没有变化，只是 pkgutil 样式命名空间包 mymeta 的 __init__.py 都消失了：

project_alpha/
   -> mymeta/
        -> project_alpha/
             -> __init__.py
             -> version.py
   -> setup.py

project_bravo/
   -> mymeta/
        -> project_bravo/
             -> __init__.py
             -> version.py
   -> setup.py

为了让 setuptools 满意，还需要调整两个安装脚本：

...
setup(
    ...
    packages=['mymeta.' + pkg for pkg in find_packages('mymeta')],
)

现在在构建 project-bravo 时可以正确解析导入。

同一命名空间中的包：无法在安装脚本中导入模块

Packages in same namespace: can't import module in setup script

python

setuptools

namespace-package