Instruction generator

lexer.py

def get_instructions(pattern_list):
    """Takes a list of regex patterns and compiles them to a list of VM
    instructions via the lexc tool, and then returns that list."""
    # The lexing compiler should be in the same folder as us
    lexexec = os.path.abspath(os.path.join(sys.path[0], "lexc"))
    # (Yes, this giant chain of os.path things checks that)
    if not os.path.isfile(os.path.abspath(os.path.join(sys.path[0], "lexc"))):
        print lexexec
        raise IOError("Lexc executable not in same folder as program.")
    command = [lexexec] + ["--pattern=%s" % str(pattern)
                           for pattern in pattern_list]
    # Raw output from lexc
    raw_inst = subprocess.check_output(command)
    # Matches properly formatted lines, grouping instructions
    # and their parameters
    inst_match = re.compile(
        r"\s+(?P<line>\d+)\s+(?P<inst>MATCH|JMP|SPLIT|CHAR)\s*(?P<a>\d+)?(?:, (?P<b>\d+))?")

    # We ignore the last line here because it will always be blank
    return [re.match(inst_match, line).groupdict()
            for line in raw_inst.split("\n")[0:-1]]