Node.toprettyxml（）在Python中向DOCTYPE添加换行符

时间：2011-12-30 23:29:44

标签： python xml pretty-print elementtree minidom

使用prettify时，我的DOCTYPE分为三行。我怎么能把它放在一条线上？

“破碎”输出：

<?xml version="1.0" encoding="utf-8"?>
<!DOCTYPE smil
  PUBLIC '-//W3C//DTD SMIL 2.0//EN'
  'http://www.w3.org/2001/SMIL20/SMIL20.dtd'>
<smil xmlns="http://www.w3.org/2001/SMIL20/Language">
  <head>
    <meta base="rtmp://cp23636.edgefcs.net/ondemand"/>
  </head>
  <body>
    <switch>
      <video src="mp4:soundcheck/1/clay_aiken/02_sc_ca_sorry_256.mp4" system-bitrate="336000"/>
      <video src="mp4:soundcheck/1/clay_aiken/02_sc_ca_sorry_512.mp4" system-bitrate="592000"/>
      <video src="mp4:soundcheck/1/clay_aiken/02_sc_ca_sorry_768.mp4" system-bitrate="848000"/>
      <video src="mp4:soundcheck/1/clay_aiken/02_sc_ca_sorry_1128.mp4" system-bitrate="1208000"/>
    </switch>
  </body>
</smil>

剧本：

import csv
import sys
import os.path

from xml.etree import ElementTree
from xml.etree.ElementTree import Element, SubElement, Comment, tostring

from xml.dom import minidom

def prettify(doctype, elem):
    """Return a pretty-printed XML string for the Element.
    """
    rough_string = doctype + ElementTree.tostring(elem, 'utf-8')
    reparsed = minidom.parseString(rough_string)
    return reparsed.toprettyxml(indent="  ", encoding = 'utf-8')

doctype = '<!DOCTYPE smil PUBLIC "-//W3C//DTD SMIL 2.0//EN" "http://www.w3.org/2001/SMIL20/SMIL20.dtd">'

video_data = ((256, 336000),
              (512, 592000),
              (768, 848000),
              (1128, 1208000))


with open(sys.argv[1], 'rU') as f:
    reader = csv.DictReader(f)
    for row in reader:
        root = Element('smil')
        root.set('xmlns', 'http://www.w3.org/2001/SMIL20/Language')
        head = SubElement(root, 'head')
        meta = SubElement(head, 'meta base="rtmp://cp23636.edgefcs.net/ondemand"')
        body = SubElement(root, 'body')

        switch_tag = ElementTree.SubElement(body, 'switch')

        for suffix, bitrate in video_data:
            attrs = {'src': ("mp4:soundcheck/{year}/{id}/{file_root_name}_{suffix}.mp4"
                             .format(suffix=str(suffix), **row)),
                     'system-bitrate': str(bitrate),
                     }
            ElementTree.SubElement(switch_tag, 'video', attrs)

        file_root_name = row["file_root_name"]
        year = row["year"]
        id = row["id"]
        path = year+'-'+id

        file_name = row['file_root_name']+'.smil'
        full_path = os.path.join(path, file_name)
        output = open(full_path, 'w')
        output.write(prettify(doctype, root))

3 个答案:

答案 0 :(得分：2)

我认为你至少有三个选择：

  1. 只需接受换行符即可。它们可能是不受欢迎的，但是它们完全合法。

  2. 添加一个用更好的DOCTYPE替换坏的DOCTYPE的kludge。也许是这样的：

       
    import re

pretty_xml = prettify(doctype, elem)
m = re.search("(<!.*dtd'>)", pretty_xml, re.DOTALL)
ugly_doctype = m.group() 
fixed_xml = pretty_xml.replace(ugly_doctype, doctype)

  3. 使用功能更丰富的XML包。 lxml浮现在脑海中;它主要与ElementTree兼容。通过使用lxml的tostring函数，您将不需要prettify函数，并且DOCTYPE会根据您的需要出现。例如：

       
    from lxml import etree 

doctype = '<!DOCTYPE smil PUBLIC "-//W3C//DTD SMIL 2.0//EN" "http://www.w3.org/2001/SMIL20/SMIL20.dtd">'

XML = '<smil xmlns="http://www.w3.org/2001/SMIL20/Language"><head><meta base="rtmp://cp23636.edgefcs.net/ondemand"/></head><body><switch><video src="mp4:soundcheck/1/clay_aiken/02_sc_ca_sorry_256.mp4" system-bitrate="336000"/><video src="mp4:soundcheck/1/clay_aiken/02_sc_ca_sorry_512.mp4" system-bitrate="592000"/><video src="mp4:soundcheck/1/clay_aiken/02_sc_ca_sorry_768.mp4" system-bitrate="848000"/><video src="mp4:soundcheck/1/clay_aiken/02_sc_ca_sorry_1128.mp4" system-bitrate="1208000"/></switch></body></smil>'

elem = etree.fromstring(XML)
print etree.tostring(elem, doctype=doctype, pretty_print=True,
                     xml_declaration=True, encoding="utf-8")

    输出：

    <?xml version='1.0' encoding='utf-8'?>
<!DOCTYPE smil PUBLIC "-//W3C//DTD SMIL 2.0//EN" "http://www.w3.org/2001/SMIL20/SMIL20.dtd">
<smil xmlns="http://www.w3.org/2001/SMIL20/Language">
  <head>
    <meta base="rtmp://cp23636.edgefcs.net/ondemand"/>
  </head>
  <body>
    <switch>
      <video src="mp4:soundcheck/1/clay_aiken/02_sc_ca_sorry_256.mp4" system-bitrate="336000"/>
      <video src="mp4:soundcheck/1/clay_aiken/02_sc_ca_sorry_512.mp4" system-bitrate="592000"/>
      <video src="mp4:soundcheck/1/clay_aiken/02_sc_ca_sorry_768.mp4" system-bitrate="848000"/>
      <video src="mp4:soundcheck/1/clay_aiken/02_sc_ca_sorry_1128.mp4" system-bitrate="1208000"/>
    </switch>
  </body>
</smil>

答案 1 :(得分：2)

查看了您当前的脚本以及您就此主题提出的其他问题，我认为您可以通过使用字符串操作构建smil文件来简化您的生活。

您文件中的几乎所有xml都是静态的。您需要担心正确处理的唯一数据是video标记的属性值。为此，标准库中有一个方便的功能，可以完全按照您的要求执行：xml.sax.saxutils.quoteattr。

因此，考虑到这些要点，这里的脚本应该更容易使用：

import sys, os, csv
from xml.sax.saxutils import quoteattr

smil_header = '''\
<?xml version="1.0" encoding="utf-8"?>
<!DOCTYPE smil PUBLIC "-//W3C//DTD SMIL 2.0//EN" "http://www.w3.org/2001/SMIL20/SMIL20.dtd">
<smil xmlns="http://www.w3.org/2001/SMIL20/Language">
  <head>
    <meta base="rtmp://cp23636.edgefcs.net/ondemand"/>
  </head>
  <body>
    <switch>
'''
smil_video = '''\
      <video src=%s system-bitrate=%s/>
'''
smil_footer = '''\
    </switch>
  </body>
</smil>
'''

src_format = 'mp4:soundcheck/%(year)s/%(id)s/%(file_root_name)s_%(suffix)s.mp4'

video_data = (
    ('256', '336000'), ('512', '592000'),
    ('768', '848000'), ('1128', '1208000'),
    )

root = os.getcwd()
if len(sys.argv) > 2:
    root = sys.argv[2]

with open(sys.argv[1], 'rU') as stream:

    for row in csv.DictReader(stream):
        smil = [smil_header]
        for suffix, bitrate in video_data:
            row['suffix'] = suffix
            smil.append(smil_video % (
                quoteattr(src_format) % row, quoteattr(bitrate)
                ))
        smil.append(smil_footer)

        directory = os.path.join(root, '%(year)s-%(id)s' % row)
        try:
            os.makedirs(directory)
        except OSError:
            pass
        path = os.path.join(directory, '%(file_root_name)s.smil' % row)
        print ':: writing file:', path
        with open(path, 'wb') as stream:
            stream.write(''.join(smil))

答案 2 :(得分：0)

我认为不可能删除Node.toprettyxml为DOCTYPE生成的换行符，至少以Pythonic方式删除。

这是writexml类的DocumentType方法，它从minidom module的第1284行开始，它插入有问题的换行符。插入的换行符字符串最初来自Node.toprettyxml方法，并通过writexml类的Document方法传递。相同的换行符字符串也会传递给writexml的各种其他子类的Node方法。在调用Node.prettyxml时更改换行符字符串将更改输出XML中使用的换行符字符串。

有各种各样的hacky方法：修改minidom模块的本地副本，'monkey-patch'writexml类的DocumentType方法或者后处理XML用于删除不需要的换行符的字符串。但是，这些方法都不适合我。

对我而言，最好的方法似乎是保持原样。将DOCTYPE拆分为多行真的是一个严重的问题吗？

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