python - Size of an open file object

Question

Is there a way to find the size of a file object that is currently open?

Specifically, I am working with the tarfile module to create tarfiles, but I don't want my tarfile to exceed a certain size. As far as I know, tarfile objects are file-like objects, so I imagine a generic solution would work.

Answer 1

$ ls -la chardet-1.0.1.tgz
-rwxr-xr-x 1 vinko vinko 179218 2008-10-20 17:49 chardet-1.0.1.tgz
$ python
Python 2.5.1 (r251:54863, Jul 31 2008, 22:53:39)
[GCC 4.1.2 (Ubuntu 4.1.2-0ubuntu4)] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> f = open('chardet-1.0.1.tgz','rb')
>>> f.seek(0,2)
>>> f.tell()
179218L

Adding ChrisJY's idea to the example

>>> import os
>>> os.fstat(f.fileno()).st_size
179218L
>>>        

Note: Based on the comments, f.seek(0, 2) is must before calling f.tell(), without which it would return a size of 0. The reason is that f.seek(0, 2) moves the file object's position to the end of the file.