[Python-Dev] open('/dev/null').read() -> MemoryError

Armin Rigo arigo at tunes.org
Mon Sep 27 22:05:33 CEST 2004


On my system, which is admittedly an old Linux box (2.2 kernel), one test

>>> file('/dev/null').read()
Traceback (most recent call last):
  File "<stdin>", line 1, in ?

This is because:

>>> os.stat('/dev/null').st_size

This looks very broken indeed.  I have no idea where this number comes from.  
I'd also complain if I was asked to allocate a buffer large enough to hold
that many bytes.  If we cared, we could "enhance" the file.read() method to
account for the possibility that maybe stat() lied; maybe it is desirable,
instead of allocating huge amounts of memory, to revert to something like the
following above some large threshold:

result = []
while 1:
  buf = f.read(16384)
  if not buf:
    return ''.join(result)

Of course for genuinely large reads it's a disaster to have to allocate twice
as much memory.  Anyway I'm not sure we care about going around broken
behaviour.  I'm just wondering if os.stat() could lie in other situations too.


More information about the Python-Dev mailing list