file existence checking

[Fredrik Lundh]

"john peter" <neuzhoundxx at yahoo.com> wrote:
> does anyone have a suggestion on simplest way to check for the existence of a file
>   within the same directory where a python script was started without really opening
>   it?

it's not like opening a file is a very expensive or dangerous operation, but
you can use

    import os

    if os.path.isfile(filename):
        print "a file named", filename, "exists"

or

    if os.path.exists(filename):
        print "something named", filename, "exists"

to check for a file.  however, if you plan to open the file later on, it's better
to just open it, and deal with the exception; e.g.

    try:
        f = open(filename)
    except IOError:
        print "failed to open", filename
        sys.exit(1)

    data = f.read(100)

</F>