Python sys.executable is empty

Question

我正在测试用os.execve和虚拟环境做一些恶作剧。如果我用另一个python子进程替换当前python进程，就会遇到sys.executable为空的问题。

下面的示例显示了正在进行的操作（在python shell中运行此操作）：

import os, sys
print(sys.executable) # works this time
os.execve("/usr/bin/python", [], {}) # drops me into a new python shell
import sys # yes, again
print(sys.executable) # is empty

我在python shell中运行上述命令的完整输出：

 lptp [ tmp ]: python
Python 2.7.10 (default, Oct 14 2015, 16:09:02) 
[GCC 5.2.1 20151010] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> import os, sys
>>> print(sys.executable) # works this time
/usr/bin/python
>>> os.execve("/usr/bin/python", [], {}) # drops me into a new python shell
Python 2.7.10 (default, Oct 14 2015, 16:09:02) 
[GCC 5.2.1 20151010] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> import sys # yes, again
>>> print(sys.executable) # is empty

>>>

sys.executable为空会引起我的问题，最明显的是，platform.libc_ver()失败，因为sys.executable为空：

>>> import platform
>>> platform.libc_ver()
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/usr/lib/python2.7/platform.py", line 163, in libc_ver
    f = open(executable,'rb')
IOError: [Errno 21] Is a directory: '/tmp'

注意，上面的示例是在调用os.execve(...)之后运行的