python - 如何从 PyYAML 异常中获取详细信息？

Question

我想优雅地通知用户他们搞砸的 YAML 文件的确切位置。 python-3.4.1/lib/python-3.4/yaml/scanner.py的第288行报告了一个常见的解析错误，并通过抛出异常进行处理:

raise ScannerError("while scanning a simple key", key.mark,
                   "could not found expected ':'", self.get_mark())

我正在纠结如何举报。

try:
    parsed_yaml = yaml.safe_load(txt)

except yaml.YAMLError as exc:
    print ("scanner error 1")
    if hasattr(exc, 'problem_mark'):
        mark = exc.problem_mark
        print("Error parsing Yaml file at line %s, column %s." %
                                            (mark.line, mark.column+1))
    else:
        print ("Something went wrong while parsing yaml file")
    return

这给出了

$ yaml_parse.py
scanner error 1
Error parsing Yaml file line 1508, column 9.

但是我如何获取错误文本以及 key.mark 和其他标记中的内容？

更有用的是，我如何检查 PyYaml 源代码来解决这个问题？ ScannerError 类似乎忽略了参数(来自 scanner.py 第 32 行):

class ScannerError(MarkedYAMLError):
     pass

Answer 1

根据@Anthon 的回答，这段代码运行良好:

try:
    import yaml
except:
    print ('Fatal error:  Yaml library not available')
    quit()

f = open ('y.yml')
txt = f.read()

try:
    yml = yaml.load(txt, yaml.SafeLoader)

except yaml.YAMLError as exc:
    print ("Error while parsing YAML file:")
    if hasattr(exc, 'problem_mark'):
        if exc.context != None:
            print ('  parser says\n' + str(exc.problem_mark) + '\n  ' +
                str(exc.problem) + ' ' + str(exc.context) +
                '\nPlease correct data and retry.')
        else:
            print ('  parser says\n' + str(exc.problem_mark) + '\n  ' +
                str(exc.problem) + '\nPlease correct data and retry.')
    else:
        print ("Something went wrong while parsing yaml file")
    return

# make use of `yml`

带有轻微破坏数据的示例输出:

$ yaml_parse.py
Error while parsing YAML file:
  parser says
  in "<unicode string>", line 1525, column 9:
      - name: Curve 1
            ^
  could not found expected ':' while scanning a simple key
Please correct data and retry.

---

$ yaml_parse.py
Error while parsing YAML file:
  parser says
  in "<unicode string>", line 1526, column 10:
        curve: title 1
             ^
  mapping values are not allowed here
Please correct data and retry.