how long a Str can be used in this python code segment?

[Stephen.Wu]

On Feb 1, 5:26 pm, Chris Rebert <c... at rebertia.com> wrote:
> On Mon, Feb 1, 2010 at 1:17 AM, Stephen.Wu <54wut... at gmail.com> wrote:
> > tmp=file.read() (very huge file)
> > if targetStr in tmp:
> >    print "find it"
> > else:
> >    print "not find"
> > file.close()
>
> > I checked if file.read() is huge to some extend, it doesn't work, but
> > could any give me some certain information on this prolbem?
>
> If the file's contents is larger than available memory, you'll get a
> MemoryError. To avoid this, you can read the file in by chunks (or if
> applicable, by lines) and see if each chunk/line matches.
>
> Cheers,
> Chris
> --http://blog.rebertia.com

actually, I just use file.read(length) way, i just want to know what
exactly para of length I should set, I'm afraid length doesn't equal
to the amount of physical memory after trials...