This function helps you do not see errors during upload solutions, because you forget to switch back to sys.stdin and also you can easily debug your code with ipdb or another python debuggers

fopen.py

def fopen(filename, default=sys.stdin):
    """
    This function helps you do not see errors during upload solutions
    because you forget to switch back to sys.stdin and also you can easily
    debug your code with ipdb or another python debuggers
    """
    try:
        f = open(filename)
    except FileNotFoundError:
        f = default
    return f