What exactly does tell() return, and how do I use it to calculate percent of file read?

Question

I am using Python 2.7 on Windows, and I am very new to Python so forgive me if this is an easy one.

Everything that I have read says that tell() returns the "position", which I believe is basically the cursor position that we are currently at in the read. OK, that sounds helpful, but I cannot figure out how to find the total "positions" of the file to calculate a percentage.

Answer 1

You could seek to the end of the file, then call .tell():

import os

fileobj.seek(0, os.SEEK_END)
size = fileobj.tell()
fileobj.seek(0, os.SEEK_SET)

The above example uses the os.SEEK_* constants to set how to interpret the seek offset (the first argument to .seek()).

or you can use the os.fstat() function to retrieve the size of your open file:

import os

size = os.fstat(fileobj.fileno()).st_size

The latter information can be more easily cached by the OS so will often be faster.