Using StopIteration

[tkpmep]

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(line)

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(line)

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]

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

 

[Steve R. Hastings]

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)

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(line)
break

 

[vbgunz]

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

 

[vbgunz]

to catch and recover from StopIterations, use this:

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

 

[tkpmep]

This is just what the doctor ordered. Thanks, as always, everyone!