PyWhich

Tim Chase python.list at tim.thechases.com
Thu Aug 4 20:24:13 CEST 2011


On 08/04/2011 07:43 AM, Billy Mays wrote:
> Hey c.l.p.,
>
> I wrote a little python script that finds the file that a python module
> came from.  Does anyone see anything wrong with this script?
>
> #!/usr/bin/python
>
> import sys
> if __name__ == '__main__':
>       if len(sys.argv)>  1:
>           try:
>               m = __import__(sys.argv[1])
>               sys.stdout.write(m.__file__ + '\n')

For a quick script in a controlled environment, not bad.  In a 
hostile environment, I'd be nervous about running arbitrary 
module code triggered by the import.  Even if non-malicious, some 
imports (like PyCrypto) may have some initialization lag which 
would be nice to avoid.  I think I'd make use of imp.find_module 
to write it something like this (untested)

   from sys import argv, stderr
   import imp
   type_map = {
     imp.PY_SOURCE: "Source file",
     imp.PY_COMPILED: "Compiled code object",
     imp.C_EXTENSION: "Dynamically loadabld shared library",
     imp.PKG_DIRECTORY: "Package directory",
     imp.C_BUILTIN: "Built-in",
     imp.PY_FROZEN: "Frozen module",
     }
   if __name__ == '__main__':
     if len(argv) > 1:
       for modname in argv[1:]:
         try:
           fp, pth, desc = imp.find_module(modname)
           (suffix, mode, type_) = desc
           if fp is not None: fp.close()
           print("%s\t[%s]" % (
             pth,
             type_map.get(type_, "UNKNOWN")
             ))
         except ImportError:
           stderr.write("No such module '%s'\n" % modname)
     else:
       stderr.write("Usage: pywhich <module> [<module>...]\n")

I don't know a good way to tap into other import hooks (such as 
the zipfile import) to augment that type_map dictionary.

-tkc






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