虚拟环境中的pyc文件将被创建为符号链接的条件是什么？

Question

我们的部署环境中有一个虚拟环境，其中.pyc文件是sym链接，特别是在<venv_root>/lib/python2.7/中。这种情况是在什么情况下发生的？

我们的环境：

• CentOS 7
• Python 2.7.5
• virtualenv 16.0.0
• 一些(但不是所有) python进程运行在其他服务器上，这些服务器通过NFS (具有写权限)提供了virtualenv。
• 在与根文件系统不同的文件系统上创建的虚拟化

我习惯于看到.py文件在<venv_root>/lib/python2.7/中有时是符号链接。我知道我可以使用--always-copy标志来阻止.py文件是符号链接。但是我已经习惯了.pyc文件总是普通的文件。

我尝试过的实验(在这个服务器上)：

• 在根文件系统上创建新的虚拟环境
  • 作为文件创建的pyc文件

​

• 在NFS主机和NFS客户端上使用虚拟主机运行脚本
  • 不更改pyc文件

​

• 触摸lib/python2.7/os.py和重新运行脚本
  • 不更改pyc文件

​

• 删除lib/python2.7/os.pyc并重新运行脚本
  • 在NFS主机上运行，则pyc文件作为普通文件创建。
  • 在NFS客户端上运行，则pyc文件作为普通文件创建。

​

重复一个关键的问题--在什么条件下，.pyc文件将成为sym链接？

以下是所讨论的虚拟目录的完整列表：

[root@appname-master]# ls -l /export/appname/common/venv/5_4_1/lib/python2.7/
total 68
lrwxrwxrwx   1 appname appname    31 Nov  8 04:17 _abcoll.py -> /usr/lib64/python2.7/_abcoll.py
lrwxrwxrwx   1 appname appname    62 Nov  8 04:17 _abcoll.pyc -> /usr/local/company/appname/venv/lib/python2.7/_abcoll.pyc
lrwxrwxrwx   1 appname appname    27 Nov  8 04:17 abc.py -> /usr/lib64/python2.7/abc.py
lrwxrwxrwx   1 appname appname    58 Nov  8 04:17 abc.pyc -> /usr/local/company/appname/venv/lib/python2.7/abc.pyc
lrwxrwxrwx   1 appname appname    30 Nov  8 04:17 codecs.py -> /usr/lib64/python2.7/codecs.py
lrwxrwxrwx   1 appname appname    61 Nov  8 04:17 codecs.pyc -> /usr/local/company/appname/venv/lib/python2.7/codecs.pyc
lrwxrwxrwx   1 appname appname    27 Nov  8 04:17 config -> /usr/lib64/python2.7/config
lrwxrwxrwx   1 appname appname    32 Nov  8 04:17 copy_reg.py -> /usr/lib64/python2.7/copy_reg.py
lrwxrwxrwx   1 appname appname    63 Nov  8 04:17 copy_reg.pyc -> /usr/local/company/appname/venv/lib/python2.7/copy_reg.pyc
lrwxrwxrwx   1 appname appname    60 Nov  8 04:17 distutils -> /usr/local/company/appname/venv/lib/python2.7/distutils
lrwxrwxrwx   1 appname appname    30 Nov  8 04:17 encodings -> /usr/lib64/python2.7/encodings
lrwxrwxrwx   1 appname appname    31 Nov  8 04:17 fnmatch.py -> /usr/lib64/python2.7/fnmatch.py
lrwxrwxrwx   1 appname appname    62 Nov  8 04:17 fnmatch.pyc -> /usr/local/company/appname/venv/lib/python2.7/fnmatch.pyc
lrwxrwxrwx   1 appname appname    35 Nov  8 04:17 genericpath.py -> /usr/lib64/python2.7/genericpath.py
lrwxrwxrwx   1 appname appname    66 Nov  8 04:17 genericpath.pyc -> /usr/local/company/appname/venv/lib/python2.7/genericpath.pyc
lrwxrwxrwx   1 appname appname    32 Nov  8 04:17 lib-dynload -> /usr/lib64/python2.7/lib-dynload
lrwxrwxrwx   1 appname appname    33 Nov  8 04:17 linecache.py -> /usr/lib64/python2.7/linecache.py
lrwxrwxrwx   1 appname appname    64 Nov  8 04:17 linecache.pyc -> /usr/local/company/appname/venv/lib/python2.7/linecache.pyc
lrwxrwxrwx   1 appname appname    30 Nov  8 04:17 locale.py -> /usr/lib64/python2.7/locale.py
lrwxrwxrwx   1 appname appname    61 Nov  8 04:17 locale.pyc -> /usr/local/company/appname/venv/lib/python2.7/locale.pyc
-rw-rw-r--+  1 appname appname     0 Nov  8 04:17 no-global-site-packages.txt
lrwxrwxrwx   1 appname appname    30 Nov  8 04:17 ntpath.py -> /usr/lib64/python2.7/ntpath.py
-rw-rw-r--+  1 appname appname     4 Nov  8 04:17 orig-prefix.txt
lrwxrwxrwx   1 appname appname    26 Nov  8 04:17 os.py -> /usr/lib64/python2.7/os.py
lrwxrwxrwx   1 appname appname    57 Nov  8 04:17 os.pyc -> /usr/local/company/appname/venv/lib/python2.7/os.pyc
lrwxrwxrwx   1 appname appname    33 Nov  8 04:17 posixpath.py -> /usr/lib64/python2.7/posixpath.py
lrwxrwxrwx   1 appname appname    64 Nov  8 04:17 posixpath.pyc -> /usr/local/company/appname/venv/lib/python2.7/posixpath.pyc
lrwxrwxrwx   1 appname appname    26 Nov  8 04:17 re.py -> /usr/lib64/python2.7/re.py
lrwxrwxrwx   1 appname appname    57 Nov  8 04:17 re.pyc -> /usr/local/company/appname/venv/lib/python2.7/re.pyc
drwxrwxr-x+ 40 appname appname  4096 Nov  8 04:17 site-packages
-rw-rw-r--+  1 appname appname 29021 Nov  8 04:17 site.py
-rw-rw-r--+  1 appname appname 26716 Nov  8 04:17 site.pyc
lrwxrwxrwx   1 appname appname    35 Nov  8 04:17 sre_compile.py -> /usr/lib64/python2.7/sre_compile.py
lrwxrwxrwx   1 appname appname    66 Nov  8 04:17 sre_compile.pyc -> /usr/local/company/appname/venv/lib/python2.7/sre_compile.pyc
lrwxrwxrwx   1 appname appname    37 Nov  8 04:17 sre_constants.py -> /usr/lib64/python2.7/sre_constants.py
lrwxrwxrwx   1 appname appname    68 Nov  8 04:17 sre_constants.pyc -> /usr/local/company/appname/venv/lib/python2.7/sre_constants.pyc
lrwxrwxrwx   1 appname appname    33 Nov  8 04:17 sre_parse.py -> /usr/lib64/python2.7/sre_parse.py
lrwxrwxrwx   1 appname appname    64 Nov  8 04:17 sre_parse.pyc -> /usr/local/company/appname/venv/lib/python2.7/sre_parse.pyc
lrwxrwxrwx   1 appname appname    27 Nov  8 04:17 sre.py -> /usr/lib64/python2.7/sre.py
lrwxrwxrwx   1 appname appname    28 Nov  8 04:17 stat.py -> /usr/lib64/python2.7/stat.py
lrwxrwxrwx   1 appname appname    59 Nov  8 04:17 stat.pyc -> /usr/local/company/appname/venv/lib/python2.7/stat.pyc
lrwxrwxrwx   1 appname appname    29 Nov  8 04:17 types.py -> /usr/lib64/python2.7/types.py
lrwxrwxrwx   1 appname appname    60 Nov  8 04:17 types.pyc -> /usr/local/company/appname/venv/lib/python2.7/types.pyc
lrwxrwxrwx   1 appname appname    32 Nov  8 04:17 UserDict.py -> /usr/lib64/python2.7/UserDict.py
lrwxrwxrwx   1 appname appname    63 Nov  8 04:17 UserDict.pyc -> /usr/local/company/appname/venv/lib/python2.7/UserDict.pyc
lrwxrwxrwx   1 appname appname    32 Nov  8 04:17 warnings.py -> /usr/lib64/python2.7/warnings.py
lrwxrwxrwx   1 appname appname    63 Nov  8 04:17 warnings.pyc -> /usr/local/company/appname/venv/lib/python2.7/warnings.pyc
lrwxrwxrwx   1 appname appname    35 Nov  8 04:17 _weakrefset.py -> /usr/lib64/python2.7/_weakrefset.py
lrwxrwxrwx   1 appname appname    66 Nov  8 04:17 _weakrefset.pyc -> /usr/local/company/appname/venv/lib/python2.7/_weakrefset.pyc

(我还感兴趣的是，当.pyc链接指向系统文件时，.py系统链接为什么会指向另一个虚拟主机。但我认为理解.pyc文件如何成为sym链接将是一个好的开始。)

Answer 1

毒物似乎是罪魁祸首(或者可能是它的依赖之一)。下面是在Ubuntu18.04上运行的。

% virtualenv /tmp/venv1
Running virtualenv with interpreter /usr/bin/python2
New python executable in /tmp/venv1/bin/python2
Also creating executable in /tmp/venv1/bin/python
Installing setuptools, pkg_resources, pip, wheel...done.

% source /tmp/venv1/bin/activate

% pip install tox
Collecting tox
  Using cached https://files.pythonhosted.org/packages/d0/43/2160a300e0b77a929a980f36ac7427dcef8f4ddac7a8c21e5a8baedad828/tox-3.5.3-py2.py3-none-any.whl
Collecting filelock<4,>=3.0.0 (from tox)
Collecting six<2,>=1.0.0 (from tox)
  Using cached https://files.pythonhosted.org/packages/67/4b/141a581104b1f6397bfa78ac9d43d8ad29a7ca43ea90a2d863fe3056e86a/six-1.11.0-py2.py3-none-any.whl
Collecting virtualenv>=1.11.2 (from tox)
  Using cached https://files.pythonhosted.org/packages/7c/17/9b7b6cddfd255388b58c61e25b091047f6814183e1d63741c8df8dcd65a2/virtualenv-16.1.0-py2.py3-none-any.whl
Collecting pluggy<1,>=0.3.0 (from tox)
  Using cached https://files.pythonhosted.org/packages/1c/e7/017c262070af41fe251401cb0d0e1b7c38f656da634cd0c15604f1f30864/pluggy-0.8.0-py2.py3-none-any.whl
Requirement already satisfied: setuptools>=30.0.0 in /tmp/venv1/lib/python2.7/site-packages (from tox) (40.5.0)
Collecting py<2,>=1.4.17 (from tox)
  Using cached https://files.pythonhosted.org/packages/3e/c7/3da685ef117d42ac8d71af525208759742dd235f8094221fdaafcd3dba8f/py-1.7.0-py2.py3-none-any.whl
Collecting toml>=0.9.4 (from tox)
  Using cached https://files.pythonhosted.org/packages/a2/12/ced7105d2de62fa7c8fb5fce92cc4ce66b57c95fb875e9318dba7f8c5db0/toml-0.10.0-py2.py3-none-any.whl
Installing collected packages: filelock, six, virtualenv, pluggy, py, toml, tox
Successfully installed filelock-3.0.10 pluggy-0.8.0 py-1.7.0 six-1.11.0 toml-0.10.0 tox-3.5.3 virtualenv-16.1.0

% virtualenv /tmp/venv2
Using real prefix '/usr'
New python executable in /tmp/venv2/bin/python2
Also creating executable in /tmp/venv2/bin/python
Overwriting /tmp/venv2/lib/python2.7/distutils/__init__.py with new content
Installing setuptools, pip, wheel...
done.

% ls -l /tmp/venv2/lib/python2.7/*.pyc | head
lrwxrwxrwx 1 hdowner staff    36 Nov  8 16:57 /tmp/venv2/lib/python2.7/_abcoll.pyc -> /tmp/venv1/lib/python2.7/_abcoll.pyc
lrwxrwxrwx 1 hdowner staff    32 Nov  8 16:57 /tmp/venv2/lib/python2.7/abc.pyc -> /tmp/venv1/lib/python2.7/abc.pyc
lrwxrwxrwx 1 hdowner staff    35 Nov  8 16:57 /tmp/venv2/lib/python2.7/codecs.pyc -> /tmp/venv1/lib/python2.7/codecs.pyc
lrwxrwxrwx 1 hdowner staff    37 Nov  8 16:57 /tmp/venv2/lib/python2.7/copy_reg.pyc -> /tmp/venv1/lib/python2.7/copy_reg.pyc
lrwxrwxrwx 1 hdowner staff    36 Nov  8 16:57 /tmp/venv2/lib/python2.7/fnmatch.pyc -> /tmp/venv1/lib/python2.7/fnmatch.pyc
lrwxrwxrwx 1 hdowner staff    40 Nov  8 16:57 /tmp/venv2/lib/python2.7/genericpath.pyc -> /tmp/venv1/lib/python2.7/genericpath.pyc
lrwxrwxrwx 1 hdowner staff    38 Nov  8 16:57 /tmp/venv2/lib/python2.7/linecache.pyc -> /tmp/venv1/lib/python2.7/linecache.pyc
lrwxrwxrwx 1 hdowner staff    35 Nov  8 16:57 /tmp/venv2/lib/python2.7/locale.pyc -> /tmp/venv1/lib/python2.7/locale.pyc
lrwxrwxrwx 1 hdowner staff    31 Nov  8 16:57 /tmp/venv2/lib/python2.7/os.pyc -> /tmp/venv1/lib/python2.7/os.pyc
lrwxrwxrwx 1 hdowner staff    38 Nov  8 16:57 /tmp/venv2/lib/python2.7/posixpath.pyc -> /tmp/venv1/lib/python2.7/posixpath.pyc