Python: Help with counters and writing files [duplicate]

Answer 1

# get current filenum, or 1 to start
try:
  with open('counterfile', 'r') as f:
    filenum = int(f.read())
except (IOError, ValueError):
  filenum = 1

# write next filenum for next run
with open('counterfile', 'w') as f:
  f.write(str(filenum + 1))

filename = 'file%s.txt' % filenum
with open(filename, 'w') as f:
  f.write('whatever you need\n')
  # insert all processing here, write to f

In Python 2.5, you also need a first line of from __future__ import with_statement to use this code example; in Python 2.6 or better, you don't (and you could also use a more elegant formatting solution than that % operator, but that's a very minor issue).