Using StopIteration

[tkpmep@hotmail.com]

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 =file(fn)
line = " "
while line[0] not in digits:
line = f.next()
ProcessLine(lin e)

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:
f.close()
continue

ProcessLine(lin e)

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?

Thanks in advance

Thomas Philips

[Peter Otten]

Re: Using StopIteration

tkpmep@hotmail. com wrote:
[color=blue]
> 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:[/color]
f = open(fn)
for line in f:
if line[:1] in digits:
ProcessLine(lin e)
break
f.close()

A for instead of the inner while loop makes the f.next() call implicit.
[color=blue]
> 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:[/color]
break
else:
# only if StopIteration was not triggered
# and thus break not reached
ProcessLine(lin e)
f.close()
[color=blue]
> 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?[/color]

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

Peter

[Steve R. Hastings]

Re: Using StopIteration

On Mon, 08 May 2006 11:23:28 -0700, tkpmep wrote:[color=blue]
> 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)[/color]


Here is what I suggest for you:


filenames=glob. glob("C:/*.txt")
for fn in filenames:
for line in open(fn):
if line[0] in digits:
ProcessLine(lin e)
break


--
Steve R. Hastings "Vita est"
steve@hastings. org http://www.blarg.net/~steveha

[vbgunz]

Re: Using StopIteration

sequence = ['','2']
for index, line in enumerate(seque nce):
if line.isspace(): continue
if line[:1].isdigit():
print 'index %s: starts with digit %s' % (index, line[:1])

[vbgunz]

Re: Using StopIteration

to catch and recover from StopIterations, use this:

try:
raise StopIteration
except StopIteration:
print 'caught StopIteration!' # verbose: sys.exc_info() requires
import sys

[tkpmep@hotmail.com]

Re: Using StopIteration

This is just what the doctor ordered. Thanks, as always, everyone!
[color=blue]
> By breaking out of the while loop as shown above.[/color]
[color=blue]
>
> Peter[/color]