Mark 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).
You do not need .readlines to iterate through a file by lines.
for line in f.readlines():pass
is awkward if you have 100million 100 byte lines, whereas
for line in f: pass
will read one line at a time and process before reading the next.
# 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.
for loops require an iterator. Files only come with one. So either use
a while loop or define a reusable file-block generator (untested):
def blocks(openfile, n):
while True:
block = openfile.read(n)
if len(block) == n:
yield block
else:
raise StopIteration
Terry Jan Reedy
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