Using StopIteration

[Peter Otten]

tkpmep at hotmail.com wrote:

> I create list of files, open each file in turn, skip past all the blank
> lines, and then process the first line that starts with a number (see
> code below)
> 
> filenames=glob.glob("C:/*.txt")
> for fn in filenames:
      f = open(fn)
      for line in f:
          if line[:1] in digits:
              ProcessLine(line)
              break
      f.close()

A for instead of the inner while loop makes the f.next() call implicit.

> If a file has only blank lines, the while loop terminates with a
> StopIteration. How can I just close this file andd skip to the next
> file if a StopIteration is raised? I tried the following:
> 
> filenames=glob.glob("C:/*.txt")
> for fn in filenames:
>     f =file(fn)
>     line = " "
>     while line[0] not in digits:
>         try:
>             line = f.next()
>         except StopIteration:
              break
      else:
          # only if StopIteration was not triggered
          # and thus break not reached
          ProcessLine(line)
      f.close()

> but got only a ValueError: I/O operation on closed file   for   line =
> f.next(). It appears that the continue is taking me back to the top of
> the while loop. How can I get back to the top of the for loop?

By breaking out of the while loop as shown above.
(all changes untested)

Peter