Checking whether a read will block and then learning stdin

clear-stdin.py

'''
Basic functions for clearing stdin by checking whether a
read will block.
'''

import select
import sys

def has_unread_input(stream=sys.stdin, timeout=0):
    '''
    Where stream is a readable file-descriptor, returns
    True if the given stream has input waiting to be read.
    Otherwise returns False.

    The default timeout of zero indicates that the given
    stream should be polled for input and the function
    returns immediately. Increasing the timeout will cause
    the function to wait that many seconds for the poll to
    succeed. Setting timeout to None will cause the function
    to block until it can return True.
    '''

    return stream in select.select([stream], [], [], timeout)[0]

def discard_input(stream=sys.stdin):
    '''
    Where stream is a readable file-descriptor, reads
    all available data and returns any bytes read. If no
    data is available, then an empty set of bytes is
    returned.
    '''

    data = bytearray()

    while has_unread_input(stream):
        data.extend(stream.readline())

    return bytes(data)


def refreshed_input(prompt=''):
    '''
    Clears stdin before writing the given prompt and
    waiting for input from stdin. Returns the given
    input as a string with the trailing-newline removed.
    '''

    discard_input(sys.stdin)
    try:
        return raw_input(prompt)
    except NameError:
        return input(prompt)