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          <h3 id="python">《Python 教程》授课笔记附件</h3>
<ul>
<li>讲师: 魏明择</li>
<li>时间: 2019</li>
</ul>
<h2 id="_1">文件</h2>
<h3 id="mode">mode 模式字符的含义</h3>
<table>
<thead>
<tr>
<th>字符</th>
<th>含义</th>
</tr>
</thead>
<tbody>
<tr>
<td>'r'</td>
<td>以只读方式打开(默认)</td>
</tr>
<tr>
<td>'w'</td>
<td>以只写方式打开，删除原有文件内容(如果文件不存在，则创建该文件并以只写方式打开)</td>
</tr>
<tr>
<td>'x'</td>
<td>创建一个新文件, 并以写模式打开这个文件,如果文件存在则会产生"FileExistsError"错误</td>
</tr>
<tr>
<td>'a'</td>
<td>以只写文件打开一个文件，如果有原文件则追加到文件末尾</td>
</tr>
<tr>
<td>'b'</td>
<td>用二进制模式打开</td>
</tr>
<tr>
<td>'t'</td>
<td>文本文件模式打开 (默认)</td>
</tr>
<tr>
<td>'+'</td>
<td>为更新内容打开一个磁盘文件 (可读可写)</td>
</tr>
</tbody>
</table>
<ul>
<li>缺省模式是 'rt'</li>
<li>'w+b' 可以实现二进制随机读写，当打开文件时，文件内容将被清零</li>
<li>'r+b' 以二进制读和更新模式打开文件,打开文件时不会清空文件内容</li>
<li>'r+' 以文本模式读和更新模式打开文件,打开文件时不会清空文件内容</li>
</ul>
<h4 id="python_1">python 文件常用方法:</h4>
<table>
<thead>
<tr>
<th>方法</th>
<th>说明</th>
</tr>
</thead>
<tbody>
<tr>
<td>F.close()</td>
<td>关闭文件(关闭后文件不能再读写会发生ValueError错误)</td>
</tr>
<tr>
<td>读取数据方法</td>
<td></td>
</tr>
<tr>
<td>F.read(size=-1)</td>
<td>从一个文件流中最多读取size个字符(文本文件)或字节(二进制文件),如果不给出参数，则默认读取文件中全部的内容并返回</td>
</tr>
<tr>
<td>F.readline()</td>
<td>读取一行数据, 如果到达文件尾则返回空行</td>
</tr>
<tr>
<td>F.readlines(max_chars=-1)</td>
<td>返回每行字符串的列表,max_chars为最大字符(或字节)数</td>
</tr>
<tr>
<td>写入数据方法</td>
<td></td>
</tr>
<tr>
<td>F.write(text)</td>
<td>写一个字符串到文件流中，返回写入的字符数(文本文件)或字节数(二进制文件)</td>
</tr>
<tr>
<td>F.writelines(lines)</td>
<td>将字符串的列表或字符串的列表中的内容写入文件</td>
</tr>
<tr>
<td>F.tell()</td>
<td>返回当前文件流读写指针的绝对位置(字节为单位)</td>
</tr>
<tr>
<td>F.seek(offset, whence=0)</td>
<td>改变数据流读写指针的位置，返回新的绝对位置</td>
</tr>
<tr>
<td>F.flush()</td>
<td>把写入文件对象的缓存内容写入到磁盘</td>
</tr>
</tbody>
</table>

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