python - 如果它们具有相同的名称，为什么 python 会找到模块而不是包？

Question

这是我的目录结构：

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

文件内容： 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

根/测试/test_1.py

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

root/_ init _.py - 空的
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

根/extra.py

class Class3(object):
    pass

根/根.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

我得到以下输出：

$ 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

原来问题是python解释器用来搜索包或模块的顺序：

$ 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...

根据 python 文档http://docs.python.org/2/tutorial/modules.html#the-module-search-path：“当一个名为 spam 的模块被导入时，解释器首先搜索一个内置模块那个名字。如果没有找到，它会在变量 sys.path 给出的目录列表中搜索名为 spam.py 的文件。”</p>

这意味着 python 应该查看 sys.path 索引 0 条目，获取路径 '/home/dmugtasimov/tmp/name-res' 并找到名为 root 的包，然后在此包中搜索名为 extra 的模块。但它会在 /home/dmugtasimov/tmp/name-res/root/ 目录中搜索模块根目录，然后尝试在其中找到名为 extra 的内容。它会发生什么？它不与官方文件相矛盾吗？还是搜索包的规则与搜索模块的规则不同？如果是这样，这些规则是否包含在文档中的某个地方？

更新

我把它放在这里是为了更好的格式。
为了进一步调查，请执行以下操作：

删除 root.pyc
将 root.py 重命名为 root2.py
运行 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

似乎 python 仅在最初的 4 次尝试中忽略 sys.path。

更新 2

简化版：

/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，两种情况下 sys.path 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']

但行为不同。对于 a.py，python 首先搜索包 xyz，然后搜索其中的模块 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

换句话说：

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

对于 t.py，它在与 a.py 本身相同的目录中搜索模块 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

换句话说：

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

因此，看起来“import xyz.b”是否会有所不同，具体取决于 a.py 最初是如何作为脚本加载或从另一个模块导入的。

更新 3

我提交了文档修复提案：http: //bugs.python.org/issue16891

更新 4

UPDATE 2 中描述的行为原因现在对我来说完全清楚了。

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

6.4.2. 包内引用

子模块通常需要相互引用。例如，环绕模块可能使用回声模块。事实上，这种引用非常普遍，以至于 import 语句首先在包含包中查找，然后再查找标准模块搜索路径。因此，环绕模块可以简单地使用 import echo 或 from echo import echofilter。如果在当前包（当前模块是其子模块的包）中找不到导入的模块，则导入语句会查找具有给定名称的顶级模块。

对于“python a.py”，“a”不被视为包中的模块，但对于“python t.py”，“a”被视为包“xyz”中的模块。因此，在第一种情况下，它根据 sys.path 搜索，但在第二种情况下，它在同一个包（即“xyz”）中搜索名为“xyz”的模块（换句话说，“xyz.xyz”）

您可以轻松查看是否像这样更改 a.py：

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 '__package__', __package__
print 'BEFORE import xyz.b'
import xyz.b
print 'AFTER import xyz.b'

我的输出是：

~/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

感谢@JF Sebastian 指出正确的文档位置。

更新 5

似乎还有另一个问题。如果有兴趣，请在此处关注评论：http: //bugs.python.org/issue16891

score 3 · Accepted Answer

我简化了问题中的示例，以证明只有四种解决方案是可能的：

显式相对导入from . import some_module或更多逗号from ..
相对导入（如果在包“xyz”中使用，则不带“xyz”）
绝对导入使用from __future__ import absolute_import（或使用 Python 3）
切勿在其中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 都很好且通用。这真是一个有用的问题。

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

像这样的消息

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

如果应用了任何解决方案（未注释），则所有三个示例都有效。

它可以在不使用任何子目录的情况下更加简化。

编辑： 我昨天尝试了很多测试，但我从不同版本中不一致地编写了它。对不起，答案无法重现。现在它是固定的。

score 3 · Accepted Answer

当相同的模块以不同的名称可用时，不要修改sys.path它会导致问题。见陷阱为粗心。

在代码中使用绝对或显式相对导入并从项目目录运行脚本。使用全名运行测试：

$ python -munittest root.tests.test_1

一些包确实在sys.path内部进行了修改，例如，查看如何twisted使用_preamble.py或 pypy 的autopath.py. 您可以决定它们的缺点（引入晦涩的导入问题）是否值得（允许运行脚本的更多方式）。避免修改sys.path用作库的代码，即，将其限制为测试模块和命令行脚本。

python - 如果它们具有相同的名称，为什么 python 会找到模块而不是包？

更新

更新 2

更新 3

更新 4

更新 5

2 回答 2

Related

Reference