file object and eof

[KraftDiner]

I open a file in python by
f = open('filename' , mode='rb')

how can I tell if I am at the end of file?
f.eof() isn't implmented.

How can I implement its functionallity?

Thanks.
B.

[Marc 'BlackJack' Rintsch]

Re: file object and eof

In <1155660586.941 712.114410@b28g 2000cwb.googleg roups.com>, KraftDiner
wrote:

I open a file in python by
f = open('filename' , mode='rb')
>
how can I tell if I am at the end of file?
f.eof() isn't implmented.
>
How can I implement its functionallity?

Try to read something. If the empty string is returned you are at the end
of the file. Or write a function that uses `os.path.filesi ze()` and the
`tell()` method of the file.

Ciao,
Marc 'BlackJack' Rintsch

[Grant Edwards]

Re: file object and eof

On 2006-08-15, KraftDiner <bobrien18@yaho o.comwrote:

I open a file in python by
f = open('filename' , mode='rb')
>
how can I tell if I am at the end of file?

I don't believe you can unless you try to read from the file.

f.eof() isn't implmented.
>
How can I implement its functionallity?

You don't, generally.

There's probably a better, "more Pythonic" way to accomplish
your goal, but you're going to have to tell us what it is.

--
Grant Edwards grante Yow! But was he mature
at enough last night at the
visi.com lesbian masquerade?

[KraftDiner]

Re: file object and eof


Grant Edwards wrote:

On 2006-08-15, KraftDiner <bobrien18@yaho o.comwrote:
>

I open a file in python by
f = open('filename' , mode='rb')

how can I tell if I am at the end of file?

>
I don't believe you can unless you try to read from the file.
>

f.eof() isn't implmented.

How can I implement its functionallity?

>
You don't, generally.
>
There's probably a better, "more Pythonic" way to accomplish
your goal, but you're going to have to tell us what it is.
>

how about?!:

def eof(fileobj):
curloc = fileobj.tell()
ofloc = fileobj.seek(0, 2)
fileobj.seek(cu rloc, 0)
if ofloc >= curloc:
return True
return False

[Marc 'BlackJack' Rintsch]

Re: file object and eof

In <1155668786.644 843.192830@m79g 2000cwm.googleg roups.com>, KraftDiner
wrote:

f.eof() isn't implmented.
>
How can I implement its functionallity?

>>
>You don't, generally.
>>
>There's probably a better, "more Pythonic" way to accomplish
>your goal, but you're going to have to tell us what it is.
>>

>
how about?!:
>
def eof(fileobj):
curloc = fileobj.tell()
ofloc = fileobj.seek(0, 2)
fileobj.seek(cu rloc, 0)
if ofloc >= curloc:
return True
return False

Works only for files that support `tell()` and `seek()`. What's your use
case for `eof()`?

Ciao,
Marc 'BlackJack' Rintsch

[sjdevnull@yahoo.com]

Re: file object and eof

KraftDiner wrote:

how about?!:
>
def eof(fileobj):
curloc = fileobj.tell()
ofloc = fileobj.seek(0, 2)
fileobj.seek(cu rloc, 0)
if ofloc >= curloc:
return True
return False

1. At least on python 2.3, seek always returns None--did that change in
2.4? I added a tell() in there to fix that.
2. You have your test reversed. It'll always return True as is.
3. Even if you fix that, it's limited utility depending on file mode
and whether the file object is seekable.

What's your actual problem? There's almost certainly a better way to
do it.

[Steve Holden]

Re: file object and eof

KraftDiner wrote:
[...]

how about?!:
>
def eof(fileobj):
curloc = fileobj.tell()
ofloc = fileobj.seek(0, 2)
fileobj.seek(cu rloc, 0)
if ofloc >= curloc:
return True
return False
>

Ignoring the errors in your file manipulation, think about replacing the
last three lines with

return ofloc >= curloc

regards
Steve
--
Steve Holden +44 150 684 7255 +1 800 494 3119
Holden Web LLC/Ltd http://www.holdenweb.com
Skype: holdenweb http://holdenweb.blogspot.com
Recent Ramblings http://del.icio.us/steve.holden

[Fredrik Lundh]

Re: file object and eof

KraftDiner wrote:

how about?!:
>
def eof(fileobj):
curloc = fileobj.tell()
ofloc = fileobj.seek(0, 2)
fileobj.seek(cu rloc, 0)
if ofloc >= curloc:
return True
return False

this doesn't work with text files on platforms that translates line
endings, it doesn't work with streams, it's not very efficient, and as
written, it doesn't work at all. and it's entirely pointless, since you
need to check the return value from "read" anyway.

</F>