def open_files(txtfile: str):
    """Open files with scheduler data input
    Args:
        txtfile => File containing scheduler data
    Returns:
        mylines => Scheduler data in list format for analysis
    """

    mylines = []                             # Declare an empty list named mylines.
    with open (txtfile, 'rt') as myfile: # Open inputfile for reading text data.
        for myline in myfile:                # For each line, stored as myline,
            mylines.append(myline)           # add its contents to mylines.
    return mylines