Differences between write and tempfile.write

Question

Please explain the following:

def feed(data):
  import os
  print "DATA LEN: %s" % len(data)
  f = open("copy", "w")
  f.write(data)
  f.close()
  print "FILE LEN: %s" % os.stat("copy").st_size
  t = tempfile.NamedTemporaryFile()
  t.write(data)
  print "TEMP LEN: %s" % os.stat(t.name).st_size
  t.close()

feed(x)
DATA LEN: 11004
FILE LEN: 11004
TEMP LEN: 8192

Why the difference, and can I fix temp? The end seems to be chopped.

Tested on 2.6, 2.7

Answer 1

I think you're running into the internal write buffer size. In the first case, you .close() the file before calling os.stat which effectively flushes the internal buffer. In the second case (with the tempfile ), you still have the file open when you call os.stat . Since the file is still open, some of it may still be buffered in memory until you flush it explicitly or by closing it.