import sys
import tty
import termios
import select
import datetime

def getch():
    """get next character without needing to press enter"""
    old_settings = termios.tcgetattr(sys.stdin)
    new_settings = old_settings[:]
    new_settings[3] &= ~termios.ICANON
    try:
        termios.tcsetattr(0, termios.TCSANOW, new_settings)
        ch = sys.stdin.read(1)
    finally:
        termios.tcsetattr(0, termios.TCSANOW, old_settings)
    return ch

def getch_nb(timeout):
    """gets next character in cbreak; returns false if none; cbreak must be set before"""
    ch = False
    if select.select([sys.stdin], [], [], timeout) == ([sys.stdin], [], []):
        ch = sys.stdin.read(1)
    return ch

def get_valid_char(char_list):
    """returns input if it matches a list of valid chars, else retruns False"""
    in_char = getch()
    for char in char_list:
        if in_char == char:
            return in_char
    return False

def get_pos_int():
    """returns input as int; returns False if not a positive integer"""
    try:
        in_int = int(input())
    except:
        return False
    else:
        if in_int < 1:
            return False
        return in_int

def delta_to_HM(delta):
    """returns a %H:%M string from a timedelta object"""
    mins, secs = divmod(int(delta.total_seconds()), 60)
    return str(mins).zfill(2) + ":" + str(secs).zfill(2)