使用lxml解析html

Question

我有以下html代碼

<a name="Audio-Encoders"></a>
<h1 class="chapter"><a href="ffmpeg.html#toc-Audio-Encoders">14. Audio Encoders</a></h1>

<p>A description of some of the currently available audio encoders
follows.
</p>
<a name="ac3-and-ac3_005ffixed"></a>
<h2 class="section"><a href="ffmpeg.html#toc-ac3-and-ac3_005ffixed">14.1 ac3 and     ac3_fixed</a></h2>

<p>AC-3 audio encoders.
</p>
<p>These encoders implement part of ATSC A/52:2010 and ETSI TS 102 366, as well as
the undocumented RealAudio 3 (a.k.a. dnet).
</p>
<p>The <var>ac3</var> encoder uses floating-point math, while the <var>ac3_fixed</var>
encoder only uses fixed-point integer math. This does not mean that one is
always faster, just that one or the other may be better suited to a
particular system. The floating-point encoder will generally produce better
quality audio for a given bitrate. The <var>ac3_fixed</var> encoder is not the
default codec for any of the output formats, so it must be specified explicitly
using the option <code>-acodec ac3_fixed</code> in order to use it.
</p>
<a name="AC_002d3-Metadata"></a>
<h3 class="subsection"><a href="ffmpeg.html#toc-AC_002d3-Metadata">14.1.1 AC-3     Metadata</a></h3>

<p>The AC-3 metadata options are used to set parameters that describe the audio,
but in most cases do not affect the audio encoding itself. Some of the options
do directly affect or influence the decoding and playback of the resulting
bitstream, while others are just for informational purposes. A few of the
options will add bits to the output stream that could otherwise be used for
audio data, and will thus affect the quality of the output. Those will be
indicated accordingly with a note in the option list below.
</p>
<p>These parameters are described in detail in several publicly-available
documents.
</p><ul>

如何從<hX class="foobar">之后的每個文本中提取文本？

例如， <h1 class="chapter"> h1標記后的內容是“以下是一些當前可用的音頻編碼器的說明”。

Answer 1

用途：

/*/h1/following-sibling::p
         [name(preceding-sibling::*[starts-with(name(),'h')][1])
         = 'h1'
         ]//text()

根據以下XML文檔 （從格式不正確的提供的片段bu中刪除尾隨未閉合的ul並將結果包裝到單個top元素中獲得）來評估此XPath表達式 ：

<html>
    <a name="Audio-Encoders"></a>
    <h1 class="chapter">
        <a href="ffmpeg.html#toc-Audio-Encoders">14. Audio Encoders</a>
    </h1>
    <p>A description of some of the currently available audio encoders follows. </p>
    <a name="ac3-and-ac3_005ffixed"></a>
    <h2 class="section">
        <a href="ffmpeg.html#toc-ac3-and-ac3_005ffixed">14.1 ac3 and     ac3_fixed</a>
    </h2>
    <p>AC-3 audio encoders. </p>
    <p>These encoders implement part of ATSC A/52:2010 and ETSI TS 102 366, as well as the undocumented RealAudio 3 (a.k.a. dnet). </p>
    <p>The 
        <var>ac3</var> encoder uses floating-point math, while the 
        <var>ac3_fixed</var> encoder only uses fixed-point integer math. This does not mean that one is always faster, just that one or the other may be better suited to a particular system. The floating-point encoder will generally produce better quality audio for a given bitrate. The 
        <var>ac3_fixed</var> encoder is not the default codec for any of the output formats, so it must be specified explicitly using the option 
        <code>-acodec ac3_fixed</code> in order to use it. 
    </p>
    <a name="AC_002d3-Metadata"></a>
    <h3 class="subsection">
        <a href="ffmpeg.html#toc-AC_002d3-Metadata">14.1.1 AC-3     Metadata</a>
    </h3>
    <p>The AC-3 metadata options are used to set parameters that describe the audio, but in most cases do not affect the audio encoding itself. Some of the options do directly affect or influence the decoding and playback of the resulting bitstream, while others are just for informational purposes. A few of the options will add bits to the output stream that could otherwise be used for audio data, and will thus affect the quality of the output. Those will be indicated accordingly with a note in the option list below. </p>
    <p>These parameters are described in detail in several publicly-available documents. </p>
</html>

選擇所需的文本節點 （在本例中為一個）：

A description of some of the currently available audio encoders follows.

同樣，此XPath表達式 ：

/*/h2/following-sibling::p
         [name(preceding-sibling::*[starts-with(name(),'h')][1])
         = 'h2'
         ]//text()

選擇以下文本節點 ：

AC-3 audio encoders. These encoders implement part of ATSC A/52:2010 and ETSI TS 102 366, as well as the undocumented RealAudio 3 (a.k.a. dnet). The 
        ac3 encoder uses floating-point math, while the 
        ac3_fixed encoder only uses fixed-point integer math. This does not mean that one is always faster, just that one or the other may be better suited to a particular system. The floating-point encoder will generally produce better quality audio for a given bitrate. The 
        ac3_fixed encoder is not the default codec for any of the output formats, so it must be specified explicitly using the option 
        -acodec ac3_fixed in order to use it.

最后，這個XPath表達式 ：

/*/h3/following-sibling::p
         [name(preceding-sibling::*[starts-with(name(),'h')][1])
         = 'h3'
         ]//text()

選擇以下文本節點 ：

The AC-3 metadata options are used to set parameters that describe the audio, but in most cases do not affect the audio encoding itself. Some of the options do directly affect or influence the decoding and playback of the resulting bitstream, while others are just for informational purposes. A few of the options will add bits to the output stream that could otherwise be used for audio data, and will thus affect the quality of the output. Those will be indicated accordingly with a note in the option list below. These parameters are described in detail in several publicly-available documents.

使用lxml解析html

問題描述

1 個解決方案

解決方案1
0 2012-09-23 14:58:55

使用lxml解析html

問題描述

1 個解決方案

解決方案1 0 2012-09-23 14:58:55

解決方案1
0 2012-09-23 14:58:55