En Mon, 27 Oct 2008 19:03:37 -0200, Steven Clark
<[EMAIL PROTECTED]> escribió:
On Mon, Oct 27, 2008 at 4:29 PM, Mark <[EMAIL PROTECTED]> wrote:
Hi;
I'm trying to use the struct.unpack to extract an int, int, char
struct info from a file. I'm more accustomed to the file.readlines
which works well in a 'for' construct (ending loop after reaching
EOF).
# This does OK at fetching one 10-byte string at a time:
# (4, 4, 2 ascii chars representing hex)
info1, info2, info3 = struct.unpack('<IIH', myfile.read(10))
# Now to do the entire file, putting into a loop just gives error:
# TypeError: 'int' object is not iterable
for info1, info2, info3 in struct.unpack('<IIH', myfile.read(10)):
In trying to shoehorn this into a 'for' loop I've been unsuccessful.
I also tried other variations that also didn't work but no point
wasting space. Using Python 2.5, WinXP
I usually do something like:
s = myfile.read(10)
while len(s) == 10:
info1, info2, info3 = struct.unpack('<IIH', s)
s = myfile.read(10)
#might want to check that len(s) == 0 here
Pretty clear. Another alternative, using a for statement as the OP
requested (and separating the "read" logic from the "process" part):
def chunked(f, size):
while True:
block = f.read(size)
if not block: break
yield block
for block in chunked(open(filename, 'rb'), 10):
info1, info2, info3 = struct.unpack('<IIH', block)
...
A third one:
from functools import partial
for block in iter(partial(open(filename,'rb').read, 10), ''):
...
(rather unreadable, I admit, if one isn't familiar with partial functions
and the 2-argument iter variant)
--
Gabriel Genellina
--
http://mail.python.org/mailman/listinfo/python-list
