[Tutor] checking if data files are good, readable, and exist

[Tim Golden]

Bryan Fodness wrote:
> I would like to check to see if the data files are good, readable, and 
> exist.  I have checked to see if they exist, but their is a possibility 
> that the data file might be binary, and I would like to have a sys.exit 
> for that as well.

You're going to be asked a lot of questions along the lines
of "What do you mean by binary?". I'm going to assume you
mean: has things other than ordinary letters, numbers
and punctuation in it. In today's internationalised and
Unicoded world that's a highly dodgy assumption, but I'm 
going to go with it.

To compound the crudeness of my approach, I'm going to
assume that anything > 126 is "binary" (thus dodging
the more complicated issue of the 0-31 control chars).

<code>
def is_binary (filename):
  return any (ord (c) > 126 for c in open (filename).read ())

print is_binary ("file1.txt")

</code>

Obviously, if you know any of the files is going to be
massive, you'll want to do something a bit smarter than
this.

TJG