After writing to a file, why does os.path.getsize still return the previous size?

filesize, python

Solution

Yes, Python is buffering your output. You'd be better off tracking the size yourself, something like this:

size = 0
for line in f1:
  if str(line) == '</Service>\n':
    break
  else:
    f2.write(line)
    size += len(line)
    print('size = ' + str(size))

(That might not be 100% accurate, eg. on Windows each line will gain a byte because of the `\r\n` line separator, but it should be good enough for simple chunking.)

Problem

I am trying to split up a large xml file into smaller chunks. I write to the output file and then check its size to see if its passed a threshold, but I dont think the getsize() method is working as expected. What would be a good way to get the filesize of a file that is changing in size. Ive done something like this... ``` import string import os f1 = open('VSERVICE.xml', 'r') f2 = open('split.xml', 'w') for line in f1: if str(line) == '</Service>\n': break else: f2.write(line) size = os.path.getsize('split.xml') print('size = ' + str(size)) ``` running this prints 0 as the filesize for about 80 iterations and then 4176. Does Python store the output in a buffer before actually outputting it?

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