How to write 1 byte to a binary file?

Question

I'm trying to write just one byte to a file in Python.

i = 10
fh.write( six.int2byte(i) )

Will output '0x00 0x0a'

fh.write( struct.pack('i', i) )

Will output '0x00 0x0a 0x00 0x00'

I want to write a single byte with the value 10 to the file.

Answer 1

You can just build a bytes object with that value:

with open('my_file', 'wb') as f:
    f.write(bytes([10]))

This works only in python3. If you replace bytes with bytearray it works in both python2 and 3.

Also: remember to open the file in binary mode to write bytes to it.

Answer 2

struct.pack("=b",i) (signed) and struct.pack("=B",i) (unsigned) pack an integer as a single byte which you can see in the docs for struct. ("=" is for using standard size and ignoring alignment - just in case) so you can do

import struct
i=10
with open('binfile', 'wb') as f:
    f.write(struct.pack("=B",i))