Why python finds module instead of package if they have the same name?

Question

Here is my directory structure:

/home/dmugtasimov/tmp/name-res
    root
        tests
            __init__.py
            test_1.py
        __init__.py
        classes.py
        extra.py
        root.py

File contents: root/tests/_init_.py

import os, sys
ROOT_DIRECTORY = os.path.abspath(os.path.join(os.path.dirname(__file__),
                                             '../..'))
if not sys.path or ROOT_DIRECTORY not in sys.path:
    sys.path.insert(0, ROOT_DIRECTORY)
# These imports are required for unittest to find test modules in package properly
from root.tests import test_1

root/tests/test_1.py

import unittest
from root.classes import Class1
class Tests(unittest.TestCase):
    pass

root/_init_.py - empty
root/classes.py

import os, sys
ROOT_DIRECTORY = os.path.abspath(os.path.join(os.path.dirname(__file__), '..'))
if not sys.path or ROOT_DIRECTORY not in sys.path:
    sys.path.insert(0, ROOT_DIRECTORY)

print 'sys.path:', sys.path
print 'BEFORE: import root.extra'
import root.extra
print 'AFTER: import root.extra'

class Class1(object):
    pass

class Class2(object):
    pass

root/extra.py

class Class3(object):
    pass

root/root.py

import os
import sys
ROOT_DIRECTORY = os.path.abspath(os.path.join(os.path.dirname(__file__), '..'))
if not sys.path or ROOT_DIRECTORY not in sys.path:
    sys.path.insert(0, ROOT_DIRECTORY)
from classes import Class2

---

I get following output:

$ python -m unittest tests.test_1
sys.path: ['/home/dmugtasimov/tmp/name-res', '', '/usr/local/lib/python2.7/dist-packages/tornado-2.3-py2.7.egg', '/usr/lib/python2.7', '/usr/lib/python2.7/plat-linux2', '/usr/lib/python2.7/lib-tk', '/usr/lib/python2.7/lib-old', '/usr/lib/python2.7/lib-dynload', '/usr/local/lib/python2.7/dist-packages', '/usr/local/lib/python2.7/dist-packages/setuptools-0.6c11-py2.7.egg-info', '/usr/lib/python2.7/dist-packages', '/usr/lib/python2.7/dist-packages/PIL', '/usr/lib/python2.7/dist-packages/gst-0.10', '/usr/lib/python2.7/dist-packages/gtk-2.0', '/usr/lib/python2.7/dist-packages/ubuntu-sso-client']
BEFORE: import root.extra
sys.path: ['/home/dmugtasimov/tmp/name-res', '', '/usr/local/lib/python2.7/dist-packages/tornado-2.3-py2.7.egg', '/usr/lib/python2.7', '/usr/lib/python2.7/plat-linux2', '/usr/lib/python2.7/lib-tk', '/usr/lib/python2.7/lib-old', '/usr/lib/python2.7/lib-dynload', '/usr/local/lib/python2.7/dist-packages', '/usr/local/lib/python2.7/dist-packages/setuptools-0.6c11-py2.7.egg-info', '/usr/lib/python2.7/dist-packages', '/usr/lib/python2.7/dist-packages/PIL', '/usr/lib/python2.7/dist-packages/gst-0.10', '/usr/lib/python2.7/dist-packages/gtk-2.0', '/usr/lib/python2.7/dist-packages/ubuntu-sso-client']
BEFORE: import root.extra
Traceback (most recent call last):
 File "/usr/lib/python2.7/runpy.py", line 162, in _run_module_as_main
    "__main__", fname, loader, pkg_name)
 File "/usr/lib/python2.7/runpy.py", line 72, in _run_code
    exec code in run_globals
 File "/usr/lib/python2.7/unittest/__main__.py", line 12, in <module>
    main(module=None)
 File "/usr/lib/python2.7/unittest/main.py", line 94, in __init__
    self.parseArgs(argv)
 File "/usr/lib/python2.7/unittest/main.py", line 149, in parseArgs
    self.createTests()
 File "/usr/lib/python2.7/unittest/main.py", line 158, in createTests
    self.module)
 File "/usr/lib/python2.7/unittest/loader.py", line 128, in loadTestsFromNames
    suites = [self.loadTestsFromName(name, module) for name in names]
 File "/usr/lib/python2.7/unittest/loader.py", line 91, in loadTestsFromName
    module = __import__('.'.join(parts_copy))
 File "tests/__init__.py", line 9, in <module>
    from root.tests import test_1
 File "/home/dmugtasimov/tmp/name-res/root/tests/__init__.py", line 9, in <module>
    from root.tests import test_1
 File "/home/dmugtasimov/tmp/name-res/root/tests/test_1.py", line 3, in <module>
    from root.classes import Class1
 File "/home/dmugtasimov/tmp/name-res/root/classes.py", line 9, in <module>
    import root.extra
 File "/home/dmugtasimov/tmp/name-res/root/root.py", line 6, in <module>
    from classes import Class2
ImportError: cannot import name Class2

It turns out the problem is the order used by python interpreter to search for package or module:

$ python -vv -m unittest tests.test_1
…skipped...
import root.classes # precompiled from /home/dmugtasimov/tmp/name-res/root/classes.pyc
sys.path: ['/home/dmugtasimov/tmp/name-res', '', '/usr/local/lib/python2.7/dist-packages/tornado-2.3-py2.7.egg', '/usr/lib/python2.7', '/usr/lib/python2.7/plat-linux2', '/usr/lib/python2.7/lib-tk', '/usr/lib/python2.7/lib-old', '/usr/lib/python2.7/lib-dynload', '/usr/local/lib/python2.7/dist-packages', '/usr/local/lib/python2.7/dist-packages/setuptools-0.6c11-py2.7.egg-info', '/usr/lib/python2.7/dist-packages', '/usr/lib/python2.7/dist-packages/PIL', '/usr/lib/python2.7/dist-packages/gst-0.10', '/usr/lib/python2.7/dist-packages/gtk-2.0', '/usr/lib/python2.7/dist-packages/ubuntu-sso-client']
BEFORE: import root.extra
# trying /home/dmugtasimov/tmp/name-res/root/root.so
# trying /home/dmugtasimov/tmp/name-res/root/rootmodule.so
# trying /home/dmugtasimov/tmp/name-res/root/root.py
# /home/dmugtasimov/tmp/name-res/root/root.pyc matches /home/dmugtasimov/tmp/name-res/root/root.py
…skipped...

---

According to python documentation http://docs.python.org/2/tutorial/modules.html#the-module-search-path: "When a module named spam is imported, the interpreter first searches for a built-in module with that name. If not found, it then searches for a file named spam.py in a list of directories given by the variable sys.path."

This means that python should look at sys.path index 0 entry, get path '/home/dmugtasimov/tmp/name-res' and find package named root and then search module named extra in this package. But instead it searches in /home/dmugtasimov/tmp/name-res/root/ directory for module root and then tries to find something named extra in it. What does it happen? Does not it contradict official documentation? Or are rules for searching packages different than for modules? If so, are these rules covered somewhere in documentation?

UPDATE

I put it here for better formatting.
For futher investigation do the following:

1. Remove root.pyc
2. Rename root.py to root2.py
3. Run python -vv -m unittest tests.test_1

# trying /home/dmugtasimov/tmp/name-res/root/root.so
# trying /home/dmugtasimov/tmp/name-res/root/rootmodule.so
# trying /home/dmugtasimov/tmp/name-res/root/root.py
# trying /home/dmugtasimov/tmp/name-res/root/root.pyc
# trying /home/dmugtasimov/tmp/name-res/root/extra.so
# trying /home/dmugtasimov/tmp/name-res/root/extramodule.so
# trying /home/dmugtasimov/tmp/name-res/root/extra.py

It appears python disregard sys.path only for initial 4 tries.

UPDATE 2

Simplified version:

/home/dmugtasimov/tmp/name-res3/xyz
    __init__.py
    a.py
    b.py
    t.py
    xyz.py

文件init .py,b.py和xyz.py为空
文件a.py:

import os, sys
ROOT_DIRECTORY = os.path.abspath(os.path.join(os.path.dirname(__file__), '..'))
if not sys.path or ROOT_DIRECTORY not in sys.path:
    print 'sys.path is modified in a.py'
    sys.path.insert(0, ROOT_DIRECTORY)
else:
    print 'sys.path is NOT modified in a.py'

print 'sys.path:', sys.path
print 'BEFORE import xyz.b'
import xyz.b
print 'AFTER import xyz.b'

文件t.py:

import os, sys
ROOT_DIRECTORY = os.path.abspath(os.path.join(os.path.dirname(__file__), '..'))
if not sys.path or ROOT_DIRECTORY not in sys.path:
    print 'sys.path is modified in t.py'
    sys.path.insert(0, ROOT_DIRECTORY)
else:
    print 'sys.path is NOT modified in t.py'

import xyz.a

跑:

python a.py

输出:

sys.path is modified in a.py
sys.path: ['/home/dmugtasimov/tmp/name-res3', '/home/dmugtasimov/tmp/name-res3/xyz',
 '/usr/local/lib/python2.7/dist-packages/tornado-2.3-py2.7.egg',
 '/home/dmugtasimov/tmp/name-res3/xyz', '/usr/lib/python2.7',
 '/usr/lib/python2.7/plat-linux2', '/usr/lib/python2.7/lib-tk',
 '/usr/lib/python2.7/lib-old', '/usr/lib/python2.7/lib-dynload',
 '/usr/local/lib/python2.7/dist-packages',
 '/usr/local/lib/python2.7/dist-packages/setuptools-0.6c11-py2.7.egg-info',
 '/usr/lib/python2.7/dist-packages',
 '/usr/lib/python2.7/dist-packages/PIL',
 '/usr/lib/python2.7/dist-packages/gst-0.10',
 '/usr/lib/python2.7/dist-packages/gtk-2.0',
 '/usr/lib/python2.7/dist-packages/ubuntu-sso-client']
BEFORE import xyz.b
AFTER import xyz.b

跑:

python -vv a.py

输出:

import xyz # directory /home/dmugtasimov/tmp/name-res3/xyz
# trying /home/dmugtasimov/tmp/name-res3/xyz/__init__.so
# trying /home/dmugtasimov/tmp/name-res3/xyz/__init__module.so
# trying /home/dmugtasimov/tmp/name-res3/xyz/__init__.py
# /home/dmugtasimov/tmp/name-res3/xyz/__init__.pyc matches /home/dmugtasimov/tmp/name-res3/xyz/__init__.py
import xyz # precompiled from /home/dmugtasimov/tmp/name-res3/xyz/__init__.pyc
# trying /home/dmugtasimov/tmp/name-res3/xyz/b.so
# trying /home/dmugtasimov/tmp/name-res3/xyz/bmodule.so
# trying /home/dmugtasimov/tmp/name-res3/xyz/b.py
# /home/dmugtasimov/tmp/name-res3/xyz/b.pyc matches /home/dmugtasimov/tmp/name-res3/xyz/b.py
import xyz.b # precompiled from /home/dmugtasimov/tmp/name-res3/xyz/b.pyc

跑:

python t.py

输出:

sys.path is modified in t.py
sys.path is NOT modified in a.py
sys.path: ['/home/dmugtasimov/tmp/name-res3', '/home/dmugtasimov/tmp/name-res3/xyz',
 '/usr/local/lib/python2.7/dist-packages/tornado-2.3-py2.7.egg',
 '/home/dmugtasimov/tmp/name-res3/xyz', '/usr/lib/python2.7',
 '/usr/lib/python2.7/plat-linux2', '/usr/lib/python2.7/lib-tk',
 '/usr/lib/python2.7/lib-old', '/usr/lib/python2.7/lib-dynload',
 '/usr/local/lib/python2.7/dist-packages',
 '/usr/local/lib/python2.7/dist-packages/setuptools-0.6c11-py2.7.egg-info',
 '/usr/lib/python2.7/dist-packages',
 '/usr/lib/python2.7/dist-packages/PIL',
 '/usr/lib/python2.7/dist-packages/gst-0.10',
 '/usr/lib/python2.7/dist-packages/gtk-2.0',
 '/usr/lib/python2.7/dist-packages/ubuntu-sso-client']
BEFORE import xyz.b
Traceback (most recent call last):
  File "t.py", line 9, in <module>
    import xyz.a
  File "/home/dmugtasimov/tmp/name-res3/xyz/a.py", line 11, in <module>
    import xyz.b
ImportError: No module named b

跑:

python -vv t.py

输出:

import xyz # directory /home/dmugtasimov/tmp/name-res3/xyz
# trying /home/dmugtasimov/tmp/name-res3/xyz/__init__.so
# trying /home/dmugtasimov/tmp/name-res3/xyz/__init__module.so
# trying /home/dmugtasimov/tmp/name-res3/xyz/__init__.py
# /home/dmugtasimov/tmp/name-res3/xyz/__init__.pyc matches /home/dmugtasimov/tmp/name-res3/xyz/__init__.py
import xyz # precompiled from /home/dmugtasimov/tmp/name-res3/xyz/__init__.pyc
# trying /home/dmugtasimov/tmp/name-res3/xyz/a.so
# trying /home/dmugtasimov/tmp/name-res3/xyz/amodule.so
# trying /home/dmugtasimov/tmp/name-res3/xyz/a.py
# /home/dmugtasimov/tmp/name-res3/xyz/a.pyc matches /home/dmugtasimov/tmp/name-res3/xyz/a.py
import xyz.a # precompiled from /home/dmugtasimov/tmp/name-res3/xyz/a.pyc
# trying /home/dmugtasimov/tmp/name-res3/xyz/os.so
# trying /home/dmugtasimov/tmp/name-res3/xyz/osmodule.so
# trying /home/dmugtasimov/tmp/name-res3/xyz/os.py
# trying /home/dmugtasimov/tmp/name-res3/xyz/os.pyc
# trying /home/dmugtasimov/tmp/name-res3/xyz/sys.so
# trying /home/dmugtasimov/tmp/name-res3/xyz/sysmodule.so
# trying /home/dmugtasimov/tmp/name-res3/xyz/sys.py
# trying /home/dmugtasimov/tmp/name-res3/xyz/sys.pyc
# trying /home/dmugtasimov/tmp/name-res3/xyz/xyz.so
# trying /home/dmugtasimov/tmp/name-res3/xyz/xyzmodule.so
# trying /home/dmugtasimov/tmp/name-res3/xyz/xyz.py
# /home/dmugtasimov/tmp/name-res3/xyz/xyz.pyc matches /home/dmugtasimov/tmp/name-res3/xyz/xyz.py
import xyz.xyz # precompiled from /home/dmugtasimov/tmp/name-res3/xyz/xyz.pyc
#   clear[2] __file__
#   clear[2] __package__
#   clear[2] sys
#   clear[2] ROOT_DIRECTORY
#   clear[2] __name__
#   clear[2] os
sys.path is modified in t.py
sys.path is NOT modified in a.py
sys.path: ['/home/dmugtasimov/tmp/name-res3', '/home/dmugtasimov/tmp/name-res3/xyz',
 '/usr/local/lib/python2.7/dist-packages/tornado-2.3-py2.7.egg',
 '/home/dmugtasimov/tmp/name-res3/xyz', '/usr/lib/python2.7',
 '/usr/lib/python2.7/plat-linux2', '/usr/lib/python2.7/lib-tk',
 '/usr/lib/python2.7/lib-old', '/usr/lib/python2.7/lib-dynload',
 '/usr/local/lib/python2.7/dist-packages',
 '/usr/local/lib/python2.7/dist-packages/setuptools-0.6c11-py2.7.egg-info',
 '/usr/lib/python2.7/dist-packages',
 '/usr/lib/python2.7/dist-packages/PIL',
 '/usr/lib/python2.7/dist-packages/gst-0.10',
 '/usr/lib/python2.7/dist-packages/gtk-2.0',
 '/usr/lib/python2.7/dist-packages/ubuntu-sso-client']
BEFORE import xyz.b
Traceback (most recent call last):
  File "t.py", line 9, in <module>
    import xyz.a
  File "/home/dmugtasimov/tmp/name-res3/xyz/a.py", line 11, in <module>
    import xyz.b
ImportError: No module named b

如您所见,sys.path对于两种情况都是相同的:

sys.path: ['/home/dmugtasimov/tmp/name-res3', '/home/dmugtasimov/tmp/name-res3/xyz', '/usr/local/lib/python2.7/dist-packages/tornado-2.3-py2.7.egg', '/home/dmugtasimov/tmp/name-res3/xyz', '/usr/lib/python2.7', '/usr/lib/python2.7/plat-linux2', '/usr/lib/python2.7/lib-tk', '/usr/lib/python2.7/lib-old', '/usr/lib/python2.7/lib-dynload', '/usr/local/lib/python2.7/dist-packages', '/usr/local/lib/python2.7/dist-packages/setuptools-0.6c11-py2.7.egg-info', '/usr/lib/python2.7/dist-packages', '/usr/lib/python2.7/dist-packages/PIL', '/usr/lib/python2.7/dist-packages/gst-0.10', '/usr/lib/python2.7/dist-packages/gtk-2.0', '/usr/lib/python2.7/dist-packages/ubuntu-sso-client']

但行为是不同的.对于a.py python首先搜索包xyz,并在其中搜索模块b:

import xyz # directory /home/dmugtasimov/tmp/name-res3/xyz
# trying /home/dmugtasimov/tmp/name-res3/xyz/__init__.so
# trying /home/dmugtasimov/tmp/name-res3/xyz/__init__module.so
# trying /home/dmugtasimov/tmp/name-res3/xyz/__init__.py
# /home/dmugtasimov/tmp/name-res3/xyz/__init__.pyc matches /home/dmugtasimov/tmp/name-res3/xyz/__init__.py
import xyz # precompiled from /home/dmugtasimov/tmp/name-res3/xyz/__init__.pyc
# trying /home/dmugtasimov/tmp/name-res3/xyz/b.so
# trying /home/dmugtasimov/tmp/name-res3/xyz/bmodule.so
# trying /home/dmugtasimov/tmp/name-res3/xyz/b.py
# /home/dmugtasimov/tmp/name-res3/xyz/b.pyc matches /home/dmugtasimov/tmp/name-res3/xyz/b.py
import xyz.b # precompiled from /home/dmugtasimov/tmp/name-res3/xyz/b.pyc

换一种说法:

1. 在目录sys.path [0] - > FOUND中搜索PACKAGE xyz
2. 搜索模块b在PACKAGE xyz - > FOUND中
3. 继续执行

对于t.py,它在与a.py本身相同的目录中搜索moduel xyz,然后在模块xyz中找不到模块b:

# trying /home/dmugtasimov/tmp/name-res3/xyz/xyz.so
# trying /home/dmugtasimov/tmp/name-res3/xyz/xyzmodule.so
# trying /home/dmugtasimov/tmp/name-res3/xyz/xyz.py
# /home/dmugtasimov/tmp/name-res3/xyz/xyz.pyc matches /home/dmugtasimov/tmp/name-res3/xyz/xyz.py
import xyz.xyz # precompiled from /home/dmugtasimov/tmp/name-res3/xyz/xyz.pyc

换一种说法:

1. 在目录中搜索MODULE xyz与a.py(或sys.path [1]相同的目录？) - > FOUND
2. 在MODULE xyz中搜索MODULE b - >未找到
3. 导入错误

所以看起来"import xyz.b"bahaves会有所不同,具体取决于a.py最初如何作为脚本加载或从另一个模块导入.

更新3

I filed proposal for documentation fix: http://bugs.python.org/issue16891

UPDATE 4

The reason for behavior described in UPDATE 2 is completely clear for me now.

http://docs.python.org/2/tutorial/modules.html#intra-package-references

6.4.2. Intra-package References

The submodules often need to refer to each other. For example, the surround module might use the echo module. In fact, such references are so common that the import statement first looks in the containing package before looking in the standard module search path. Thus, the surround module can simply use import echo or from echo import echofilter. If the imported module is not found in the current package (the package of which the current module is a submodule), the import statement looks for a top-level module with the given name.

For "python a.py" "a" is not considered as module in package, but for "python t.py" "a" is considered as a module in package "xyz". Therefore in first case it searches according sys.path, but in the second case it searches inside the same package (namely "xyz") for module named "xyz" (in other words "xyz.xyz")

You can easily see if change a.py like this:

File a.py:

import os, sys
ROOT_DIRECTORY = os.path.abspath(os.path.join(os.path.dirname(__file__), '..'))
if not sys.path or ROOT_DIRECTORY not in sys.path:
    print 'sys.path is modified in a.py'
    sys.path.insert(0, ROOT_DIRECTORY)
else:
    print 'sys.path is NOT modified in a.py'

print 'sys.path:', sys.path
print '__package__', __package__
print 'BEFORE import xyz.b'
import xyz.b
print 'AFTER import xyz.b'

My output was:

~/tmp/name-res3/xyz $ python a.py
sys.path is modified in a.py
sys.path: ['/home/dmugtasimov/tmp/name-res3', '/home/dmugtasimov/tmp/name-res3/xyz',
 '/usr/local/lib/python2.7/dist-packages/tornado-2.3-py2.7.egg',
 '/usr/lib/python2.7', '/usr/lib/python2.7/plat-linux2',
 '/usr/lib/python2.7/lib-tk', '/usr/lib/python2.7/lib-old',
 '/usr/lib/python2.7/lib-dynload',
 '/usr/local/lib/python2.7/dist-packages',
 '/usr/local/lib/python2.7/dist-packages/setuptools-0.6c11-py2.7.egg-info',
 '/usr/lib/python2.7/dist-packages',
 '/usr/lib/python2.7/dist-packages/PIL',
 '/usr/lib/python2.7/dist-packages/gst-0.10',
 '/usr/lib/python2.7/dist-packages/gtk-2.0',
 '/usr/lib/python2.7/dist-packages/ubuntu-sso-client']
__package__ None
BEFORE import xyz.b
AFTER import xyz.b
~/tmp/name-res3/xyz $ python t.py
sys.path is modified in t.py
sys.path is NOT modified in a.py
sys.path: ['/home/dmugtasimov/tmp/name-res3', '/home/dmugtasimov/tmp/name-res3/xyz',
 '/usr/local/lib/python2.7/dist-packages/tornado-2.3-py2.7.egg',
 '/usr/lib/python2.7', '/usr/lib/python2.7/plat-linux2',
 '/usr/lib/python2.7/lib-tk', '/usr/lib/python2.7/lib-old',
 '/usr/lib/python2.7/lib-dynload',
 '/usr/local/lib/python2.7/dist-packages',
 '/usr/local/lib/python2.7/dist-packages/setuptools-0.6c11-py2.7.egg-info',
 '/usr/lib/python2.7/dist-packages',
 '/usr/lib/python2.7/dist-packages/PIL',
 '/usr/lib/python2.7/dist-packages/gst-0.10',
 '/usr/lib/python2.7/dist-packages/gtk-2.0',
 '/usr/lib/python2.7/dist-packages/ubuntu-sso-client']
__package__ xyz
BEFORE import xyz.b
Traceback (most recent call last):
  File "t.py", line 9, in <module>
    import xyz.a
  File "/home/dmugtasimov/tmp/name-res3/xyz/a.py", line 12, in <module>
    import xyz.b
ImportError: No module named b

Thanks to @J.F. Sebastian for pointing out the right place of documentation.

UPDATE 5

It seems that there is another issue. If interested, please, follow comments here: http://bugs.python.org/issue16891

Answer 1

我简化了问题中的示例来演示只有四种解决方案是可能的：

• 显式相对导入from . import some_module或使用更多逗号from ..
• 相对导入（如果在包“xyz”中使用，则不带“xyz。”）
• 使用绝对导入from __future__ import absolute_import（或使用Python 3）
• 切勿在包内的任何路径中重复包的顶级可导入名称。

什么解决方案是最好的？这取决于个人对 Python 2 或 3 的偏好。只有最后一个对所有 Python 来说都是好的和通用的。这确实是一个有用的问题。

xyz/tests/__init__.py：import xyz.tests.t

xyz/测试/t.py：

import sys
print('sys.path = %s' % sys.path) # see that the parent of "xyz" is on sys.path
print("importing xyz.tests")
import xyz.a

xyz/a.py:

# solution A: absolute_import by __future__  (or use Python 3)
#from __future__ import absolute_import
print("importing xyz.a")
# solution B: explicit relative import
#from . import b    # and remove "import xyz.b"
# solution C: relative import (not recommended)
#import b           # and remove "import xyz.b"
import xyz.b

xyz/b.py：print("imported xyz.b")

xyz/xyz.py：print("Imported xyz.xyz !!!")

xyz/__init__.py：空文件

一切可能的失败，例如

parent_of_xyz=...  # The parent directory of "xyz" - absolute path
cd $parent_of_xyz
python -m xyz.tests.t
PYTHONPATH=$parent_of_xyz/xyz python -m unittest tests
PYTHONPATH=$parent_of_xyz     python xyz/tests/t.py

与类似的消息

Imported xyz.xyz  !!!
...
ImportError...

如果应用任何解决方案（未注释），则所有三个示例都有效。

不使用任何子目录可以更加简化。

编辑： 我昨天尝试了很多测试，但我从不同版本编写的内容不一致。抱歉，答案无法重现。现在它已经修复了。