Reading binary data from stdin

From the docs (see here):

The standard streams are in text mode by default. To write or read binary data to these, use the underlying binary buffer. For example, to write bytes to stdout, use sys.stdout.buffer.write(b'abc').

But, as in the accepted answer, invoking python with a -u is another option which forces stdin, stdout and stderr to be totally unbuffered. See the python(1) manpage for details.

See the documentation on io for more information on text buffering, and use sys.stdin.detach() to disable buffering from within Python.

Here is the final cut for Linux/Windows Python 2/3 compatible code to read data from stdin without corruption:

import sys

PY3K = sys.version_info >= (3, 0)

if PY3K:
    source = sys.stdin.buffer
else:
    # Python 2 on Windows opens sys.stdin in text mode, and
    # binary data that read from it becomes corrupted on \r\n
    if sys.platform == "win32":
        # set sys.stdin to binary mode
        import os, msvcrt
        msvcrt.setmode(sys.stdin.fileno(), os.O_BINARY)
    source = sys.stdin

b = source.read()