如何使用 xml.sax python 解析具有不同元素的 xml 文件？

Question

我正在寻找使用 python 解析大型 xml 文件。该文件包含几个不同的元素。这是我正在处理的文件的示例：

<movie title="Searching">
   <type>War, Thriller</type>
   <format>DVD</format>
   <year>2018</year>
   <rating>PG</rating>
   <stars>10</stars>
   <description>Missing girl</description>
</movie>
<song title="Need You Now">
   <type>Pop, Country</type>
   <format>MP4</format>
   <year>2010</year>
   <singer>Lady Antebellum</rating>
   <stars>8</stars>
</song>
   <movie title="Sidewalk of New York">
   <type>Romantic comedy</type>
   <format>DVD</format>
   <rating>PG</rating>
   <stars>7</stars>
   <description>Stories of people's perspective of love in NY</description>
</movie>

从上面的文件中，我想解析并存储与电影和歌曲元素相关的所有信息以列出。我正在使用 xml.sax 库，但遇到了如何区分元素的问题。例如，如果我解析类型、格式和年份标签，则无法区分它属于电影还是歌曲。这是我目前使用的一个 sn-p 代码：

import psycopg2
import xml.sax
from xml.sax.handler import ContentHandler

class MovieHandler( xml.sax.ContentHandler ):
   def __init__(self):
      self.CurrentData = ""
      self.type = ""
      self.format = ""
      self.year = ""
      self.data = {} #dict
      self.list = [] #list to store information
      self.list2 = []
      self.list3 = []
      self.list4 = []
      self.list5 = []

   # Call when an element starts
   def startElement(self, tag, attributes):
      self.CurrentData = tag
      if tag == "movie":
         title = attributes["title"]
         self.list.append(title)
         self.data['title'] = self.list
      elif tag == "song":
         title = attributes ["title"]
         self.list2.append(title)
         self.data['song_title'] = self.list2

   # Call when an elements ends
   def endElement(self, tag):
      if self.CurrentData == "type":
         type = self.type
         self.list3.append(type)
         self.data['type'] = self.list3
      elif self.CurrentData == "format":
         format = self.format
         self.list4.append(format)
         self.data['format'] = self.list4
      elif self.CurrentData == "year":
         year = int(self.year)
         self.list5.append(year)
         self.data['year'] = self.list5
      self.CurrentData = ""

   # Call when a character is read
   def characters(self, content):
      if self.CurrentData == "type":
         self.type = content
      elif self.CurrentData == "format":
         self.format = content
      elif self.CurrentData == "year":
         self.year = content

上面代码的结果是类型、格式、年份都会被重复计算。这是输出示例：

{'format': ['DVD', 'MP4', 'DVD'],
 'title': ['Searching', 'Need You Now', 'Sidewalk of New York'],
 'type': ['War, Thriller',
  'Pop, Country',
  'Romantic Comedy'],
 'year': [2018, 2010]}

关于如何解决这个问题的任何想法？谢谢！

Answer 1

您可以将当前类型保存在startElement中，然后您可以将数据相应地存储在endElement()中

def startElement(self, tag, attributes):
    if tag == "movie":
        self.currentEntryType = "movie"
    elif tag == "song":
        self.currentEntryType = "song"
    ...

def endElement(self, tag):
    if self.currentEntryType == "movie":
        ... # store as movie data

（我不太确定您的输出列表应该是什么样子，也许您可​​以为示例 xml 发布完美的输出列表）

编辑： 有 2 个字典，一个用于电影，一个用于歌曲，会更好吗？这取决于您的数据库的外观。

我完全不知道你为什么想要列表，使用字典列表而不是列表字典不是更好吗？

例如像这样使用 2 个字典：

{   
'format': ['DVD', 'DVD'],
'title': ['Searching', 'Sidewalk of New York'],
'type': ['War, Thriller', 'Romantic Comedy'],
'year': [2018]
}
{   
'format': ['MP4'],
'title': ['Need You Now'],
'type': ['Pop, Country'],
'year': [2010]
}

问题在于，您无法决定 2018 年是属于 Searching 还是属于 Sidewalk of New York。将列表提交到数据库时会出现问题吗？

这是一个包含两个 dicts 的解决方案，一个用于电影，一个用于歌曲。 基本上它使用 8 个列表而不是 5 个列表来分别存储所有内容。

class MovieHandler( xml.sax.ContentHandler ):
   def __init__(self):
      self.CurrentData = ""
      self.type = ""
      self.format = ""
      self.year = ""
      self.dataMovies = {} #dict
      self.dataSongs = {}
      self.list = [] # movie title
      self.list2 = [] # song title
      self.list3 = [] # movie type
      self.list4 = [] # movie format
      self.list5 = [] # movie year
      self.list6 = [] # song type
      self.list7 = [] # song format
      self.list8 = [] # song year

      self.currentEntryType = None

   # Call when an element starts
   def startElement(self, tag, attributes):
      self.CurrentData = tag
      if tag == "movie":
         title = attributes["title"]
         self.list.append(title)
         self.dataMovies['title'] = self.list
         self.currentEntryType = "movie"
      elif tag == "song":
         title = attributes ["title"]
         self.list2.append(title)
         self.dataSongs['song_title'] = self.list2
         self.currentEntryType = "song"

   # Call when an elements ends
   def endElement(self, tag):

      if tag == "movie":
         # Make movie lists the same length
         self.list3.extend([None]*(len(self.list)-len(self.list3)))
         self.list4.extend([None]*(len(self.list)-len(self.list4)))
         self.list5.extend([None]*(len(self.list)-len(self.list5)))   
      elif tag == "song":
         # Make movie lists the same length
         self.list6.extend([None]*(len(self.list2)-len(self.list6)))
         self.list7.extend([None]*(len(self.list2)-len(self.list7)))
         self.list8.extend([None]*(len(self.list2)-len(self.list8))) 

      if self.currentEntryType == "movie":
         if self.CurrentData == "type":
            type = self.type
            self.list3.append(type)
            self.dataMovies['type'] = self.list3
         elif self.CurrentData == "format":
            format = self.format
            self.list4.append(format)
            self.dataMovies['format'] = self.list4
         elif self.CurrentData == "year":
            year = int(self.year)
            self.list5.append(year)
            self.dataMovies['year'] = self.list5
         self.CurrentData = ""
      elif self.currentEntryType == "song":
         if self.CurrentData == "type":
            type = self.type
            self.list6.append(type)
            self.dataSongs['type'] = self.list6
         elif self.CurrentData == "format":
            format = self.format
            self.list7.append(format)
            self.dataSongs['format'] = self.list7
         elif self.CurrentData == "year":
            year = int(self.year)
            self.list8.append(year)
            self.dataSongs['year'] = self.list8
         self.CurrentData = ""

   # Call when a character is read
   def characters(self, content):
      if self.CurrentData == "type":
         self.type = content
      elif self.CurrentData == "format":
         self.format = content
      elif self.CurrentData == "year":
         self.year = content