今天折腾一上午，终于 完成了 Coursera 上 这个课程的最后一个汇编器项目。这套课程真是没白跟，收获良多，现在已经等不及想看下一期的软件部分了，哈哈。

下面是我的 python 实现，存个档，同时给同样在看这课程的同学们参考。

注释风格看起来可能有点奇怪，拍脑袋想的，没多少 python 编码经验，还望包涵，稍微解释一下：

#-----------------## 大块代码用途描述 ##-----------------### 分级注释### 分级注释#### 分级注释

import sysimport os.path#--------## tables ##--------### symbol tableSYMB_TABLE = {    "SP":     0,    "LCL":    1,    "ARG":    2,    "THIS":   3,    "THAT":   4,    "R0":     0,    "R1":     1,    "R2":     2,    "R3":     3,    "R4":     4,    "R5":     5,    "R6":     6,    "R7":     7,    "R8":     8,    "R9":     9,    "R10":    10,    "R11":    11,    "R12":    12,    "R13":    13,    "R14":    14,    "R15":    15,    "SCREEN": 16384,    "KBD":    24576}## comp tableCOMP_TABLE = {    "0":   "0101010",    "1":   "0111111",    "-1":  "0111010",    "D":   "0001100",    "A":   "0110000",    "!D":  "0001101",    "!A":  "0110001",    "-D":  "0001111",    "-A":  "0110011",    "D+1": "0011111",    "A+1": "0110111",    "D-1": "0001110",    "A-1": "0110010",    "D+A": "0000010",    "D-A": "0010011",    "A-D": "0000111",    "D&A": "0000000",    "D|A": "0010101",    "M":   "1110000",    "!M":  "1110001",    "-M":  "1110011",    "M+1": "1110111",    "M-1": "1110010",    "D+M": "1000010",    "D-M": "1010011",    "M-D": "1000111",    "D&M": "1000000",    "D|M": "1010101"}## dest tableDEST_TABLE = {    "null": "000",    "M":    "001",    "D":    "010",    "MD":   "011",    "A":    "100",    "AM":   "101",    "AD":   "110",    "AMD":  "111"}## jump tableJUMP_TABLE = {    "null": "000",    "JGT":  "001",    "JEQ":  "010",    "JGE":  "011",    "JLT":  "100",    "JNE":  "101",    "JLE":  "110",    "JMP":  "111"}#------------------## helper functions ##------------------### determine is Intdef isInt(str):    try:        int(str)        return True    except ValueError:        return False## determine instruction typedef getInsType(ins):    if ins[0] == '@':        return 'a'    return 'c'## split instruction### instruction Aram_variable_num = 16def valueOfAIns(ins):    global ram_variable_num    if SYMB_TABLE.has_key(ins[1:]):        ins = SYMB_TABLE[ins[1:]]    elif isInt(ins[1:]):        ins = ins[1:]    else:        SYMB_TABLE[ins[1:]] = ram_variable_num        ram_variable_num += 1        ins = SYMB_TABLE[ins[1:]]    bin_value =  bin(int(ins))[2:]    zero_count = 16 - len(bin_value)    zero_str =   '0' * zero_count    return zero_str + bin_value### instruction Cdef splitCIns(ins):    c_parts = {}    dest_splited = ins.split('=')    if len(dest_splited) == 1:        c_parts['dest'] = 'null'        jump_splited = dest_splited[0].split(';')    else:        c_parts['dest'] = dest_splited[0]        jump_splited = dest_splited[1].split(';')    if len(jump_splited) == 1:        c_parts['jump'] = 'null'    else:        c_parts['jump'] = jump_splited[1]    c_parts['comp'] = jump_splited[0]    return c_parts#------------## main logic ##------------### first pass### source filesf_name = sys.argv[1]sf = open(sf_name, 'r')### destination filedf_name = os.path.splitext(sf_name)[0] + ".tmp"df = open(df_name, 'w')line_num = 0for ins in sf:    # comment    ins = ins.split('//')[0]    # white space    ins = ins.strip()    if len(ins) == 0: continue    # label    if ins[0] == '(' and ins[-1] == ')':        SYMB_TABLE[ins[1:-1]] = line_num        continue    df.write(ins + '\n')    line_num += 1sf.close()df.close()## second pass### source filesf_name = os.path.splitext(sf_name)[0] + ".tmp"sf = open(sf_name, 'r')### destination filedf_name = os.path.splitext(sf_name)[0] + ".hack"df = open(df_name, 'w')for ins in sf:    ins = ins.strip()    ins_type = getInsType(ins)    if ins_type == 'a':        val = valueOfAIns(ins) + '\n'        df.write(val)    elif ins_type == 'c':        parts = splitCIns(ins)        val = '111' + COMP_TABLE[parts['comp']] + DEST_TABLE[parts['dest']] + JUMP_TABLE[parts['jump']] + '\n'        df.write(val)sf.close()df.close()