python - 同一命名空间中的包: can't import module in setup script

Question

我很好奇以下情况。假设我有两个名为 project_alpha 和 project_bravo 的项目，它们都定义了顶级命名空间包 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 仅包含行 __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。声明了命名空间包 mymeta，并从 version 模块中获取版本:

# 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 依赖于 project_alpha构建时:

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'

不幸的是，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，突然构建成功了...

---

编辑:我介绍了此问题的解决方法。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，这不是一个正确的解决方案，因此不会将其发布为答案，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，版本将被初始化，因此无需从 mymeta 包中导入任何内容。

Answer 1

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。 。项目结构几乎没有改变，只是 pkgutil 风格的命名空间包 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，两个安装脚本也需要调整:

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

现在，在构建 project-bravo 时，导入将被正确解析。