Question

我是一个试图调试脚本的Python新手。我有一个功能失败，我想知道是什么导致它失败。该函数调用一个类，如下所示：

class QueryParser(object):
    fallback = None
    other = None

    def __init__(self, tags):
        self.validate = True
        self.use_fallback = False
        self.parser_args = None
        self.db = HachoirParserList.getInstance()
        self.parsers = set(self.db)
        parsers = []
        for tag in tags:
            if not self.parsers:
                break
            parsers += self._getByTag(tag)
            if self.fallback is None:
                self.fallback = len(parsers) == 1
        if self.parsers:
            other = len(parsers)
            parsers += list(self.parsers)
            self.other = parsers[other]
        self.parsers = parsers

    def __iter__(self):
        return iter(self.parsers)

    def translate(self, name, value):
        if name == "filename":
            filename = os.path.basename(value).split(".")
            if len(filename) <= 1:
                value = ""
            else:
                value = filename[-1].lower()
            name = "file_ext"
        return name, value

    def _getByTag(self, tag):
        if tag is None:
            self.parsers.clear()
            return []
        elif callable(tag):
            parsers = [ parser for parser in self.parsers if tag(parser) ]
            for parser in parsers:
                self.parsers.remove(parser)
        elif tag[0] == "class":
            self.validate = False
            return [ tag[1] ]
        elif tag[0] == "args":
            self.parser_args = tag[1]
            return []
        else:
            tag = self.translate(*tag)
            parsers = []
            if tag is not None:
                key = tag[0]
                byname = self.db.bytag.get(key,{})
                if tag[1] is None:
                    values = byname.itervalues()
                else:
                    values = byname.get(tag[1],()),
                if key == "id" and values:
                    self.validate = False
                for value in values:
                    for parser in value:
                        if parser in self.parsers:
                            parsers.append(parser)
                            self.parsers.remove(parser)
        return parsers

    def parse(self, stream, fallback=True):
        fb = None
        warn = warning
        for parser in self.parsers:
            try:
                parser_obj = parser(stream, validate=self.validate)
                if self.parser_args:
                    for key, value in self.parser_args.iteritems():
                        setattr(parser_obj, key, value)
                return parser_obj
            except ValidateError, err:
                res = unicode(err)
                if fallback and self.fallback:
                    fb = parser
            except HACHOIR_ERRORS, err:
                res = unicode(err)
            if warn:
                if parser == self.other:
                    warn = info
                warn(_("Skip parser '%s': %s") % (parser.__name__, res))
            fallback = False
        if self.use_fallback and fb:
            warning(_("Force use of parser '%s'") % fb.__name__)
            return fb(stream)

功能是 x = QueryParser(stream.tags).parse(stream)

我已经尝试将print语句放在类中以便跟踪流但没有打印出来。我如何知道在这个类中调用哪些函数及其顺序+返回值？

Answer 1

安装pudb并从要追踪流量的点开始插入以下行：

from pudb import set_trace
set_trace()

Pudb将逐步显示正在执行的行以及局部变量的值。

新手调试Python类

1 个答案: