The on-line documentation states that os.popen is now deprecated. All other deprecated functions duly raise a DeprecationWarning. For instance:

>>> import os
>>> [c.close() for c in os.popen2('ps h -eo pid:1,command')]
__main__:1: DeprecationWarning: os.popen2 is deprecated.  Use the subprocess module.
[None, None]

The function os.popen, on the other hand, completes silently:

>>>len(list(os.popen('ps h -eo pid:1,command')))
202

Without raising a warning. Of the three possible scenarios

1. It is expected behaviour that documentation and standard library have different ideas of what is deprecated;
2. There is an error in the documentation and os.popen is not really deprecated;
3. There is an error in the standard library and os.popen should raise a warning;

which one is the correct one?

For background information, here's the Python I'm using:

>>> import sys
>>> print sys.version
2.6.2 (r262:71600, May 12 2009, 10:57:01) 
[GCC 4.2.4 (Ubuntu 4.2.4-1ubuntu3)]

The argument to os.popen is taken from a reply of mine here on Stack Overflow.

Addendum: Thanks to cobbal below, it turns out that os.popen is not deprecated in Python 3.1, after all.

Here is the PEP.

Deprecated modules and functions in the standard library:- buildtools- cfmfile- commands.getstatus()- macostools.touched()- md5- MimeWriter- mimify- popen2, os.popen[234]()- posixfile- sets- sha