I want to make my own data of types bytes in order to write it out.
For example, I want to write out the bytes 0..9

#!/usr/bin/env python3.0
foo = b''
for i in range (0,10):
    foo += i
#sys.stdout.buffer.write(foo)

Here is the error:
Traceback (most recent call last):
  File "./x.py", line 4, in <module>
    foo += i
TypeError: can't concat bytes to int

I cannot find any function to convert the int i into something
that I can append to foo. I tried chr, which produced a string
typeerror. byte() was not defined. There must be a way to convert
an integral value to a bytes type.