Reading the same file multiple times in Python

Question

Hello,

I need to download a zip archive of text files, dispatch each text file in the archive to other handlers for processing, and finally write the unzipped text file to disk.

I have the following code. It uses multiple open/close on the same file, which does not seem elegant. How do I make it more elegant and efficient?

zipped = urllib.urlopen('www.abc.com/xyz.zip')
buf = cStringIO.StringIO(zipped.read())
zipped.close()
unzipped = zipfile.ZipFile(buf, 'r')
for f_info in unzipped.infolist():
   logfile = unzipped.open(f_info)
   handler1(logfile)
   logfile.close()   ## Cannot seek(0). The file like obj does not support seek()
   logfile = unzipped.open(f_info)
   handler2(logfile)
   logfile.close()
   unzipped.extract(f_info)

Answer 1

You could say something like:

handler_dispatch(logfile)

and

def handler_dispatch(file):
   for line in file:
      handler1(line)
      handler2(line)

or even make it more dynamic by constructing a Handler class with multiple handlerN functions, and applying each of them inside handler_dispatch. Like

class Handler:
    def __init__(self:)
        self.handlers = []

  def add_handler(handler):
      self.handlers.append(handler)

  def handler_dispatch(self, file):
      for line in file:
          for handler in self.handlers:
              handler.handle(line)

Answer 2

Open the zip file once, loop through all the names, extract the file for each name and process it, then write it to disk.

Like so:

for f_info in unzipped.info_list():
    file = unzipped.open(f_info)
    data = file.read()
    # If you need a file like object, wrap it in a cStringIO
    fobj = cStringIO.StringIO(data)
    handler1(fobj)
    handler2(fobj)
    with open(filename,"w") as fp:
        fp.write(data)

You get the idea

Answer 3

Your answer is in your example code. Just use StringIO to buffer the logfile:

zipped = urllib.urlopen('www.abc.com/xyz.zip')
buf = cStringIO.StringIO(zipped.read())
zipped.close()
unzipped = zipfile.ZipFile(buf, 'r')
for f_info in unzipped.infolist():
   logfile = unzipped.open(f_info)
   # Here's where we buffer:
   logbuffer = cStringIO.StringIO(logfile.read())
   logfile.close()

   for handler in [handler1, handler2]:
      handler(logbuffer)
      # StringIO objects support seek():
      logbuffer.seek(0)

   unzipped.extract(f_info)