write binary with struct.pack_into

[Alexander Blinne]

First, you should consider reading the documentation of
struct.unpack_from and struct.pack_into at
http://docs.python.org/library/struct.html quite carefully. It says,
that these commands take a parameter called offset, which names the
location of the data in a buffer (e.g. an opened file).

example:

bloco='>%df' % (252)	        # Format string (252 floats)
fa = open('testIN.bin', 'rb')   # open for reading in binary mode
off = 0           # suppose i want to read block at beginning of file
my_array=struct.unpack_from(bloco, fa, off)  #read data


now write them to another file:

fb = open('testOUT.bin', 'r+b')   # open for updating in binary mode
off = 0           # suppose i want to write block at beginning of file
struct.pack_into(bloco, fb, off, *my_array)  #write data to testOUT