🔴 五段代码，各被哪一站拦下

五段代码：括号没关、缺冒号、函数外写 return、名字没定义、完全正常。拿一个"逐站放行"的函数跑一遍，看各自倒在哪儿：

import ast, io, tokenize

def stage_of(src):
    """这段源码在流水线的哪一站被拦下来"""
    try:
        list(tokenize.generate_tokens(io.StringIO(src).readline))
    except (tokenize.TokenError, IndentationError, SyntaxError):
        return "词法"
    try:
        ast.parse(src)
    except SyntaxError:
        return "语法"
    try:
        code = compile(src, "<s>", "exec")
    except SyntaxError:
        return "语义"
    try:
        exec(code, {})
    except NameError:
        return "运行"
    return "通过"

LEX = 'x = (1 + 2'          # 括号没关
SYN = 'if x > 1\n    y = 2'          # 缺冒号
SEM = 'return 1'          # 函数外面写 return
RUN = 'y = undefined_name'          # 名字没定义
OK  = 'y = 1 + 1'           # 完全正常

print("/".join(stage_of(s) for s in (LEX, SYN, SEM, RUN, OK)))