Python sys.executable为空

Question

我正在测试在os.execve虚拟环境中进行一些恶作剧。sys.executable如果我将当前的python进程替换为另一个python子进程，就会遇到空的问题。

以下示例显示了发生的情况（在python shell中运行）：

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中运行以上命令的完整输出：

 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空着是我的问题，最明显的是platform.libc_ver()因为sys.executable空着而失败了：

>>> 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'

请注意，上面的示例是在调用后运行的 os.execve(...)

Answer 1

Python依靠argv[0]和几个环境变量来确定sys.executable。当您传递一个空的argv和环境时，Python不知道如何确定其路径。至少，您应该提供argv[0]：

os.execve('/usr/bin/python', ['/usr/bin/python'], {})