擅长:python、mysql、java
<p><code>open</code>的默认行为是在文件不存在时引发异常。如果要执行其他操作,则需要捕获异常:</p>
<pre class="lang-py prettyprint-override"><code>try:
f = open("EMA_Script.txt", "a+")
except FileNotFoundError:
# your code to handle the case when the file doesn't exist (maybe open with write mode)
</code></pre>
<p>尽管我们在这里,但在处理文件时使用上下文是一种很好的做法,以确保它们始终处于关闭状态——事实上,任何需要关闭的文件(如数据库连接)都应该这样做。原因是,即使在<code>open</code>和<code>close</code>之间发生异常,上下文也会确保文件已关闭</p>
<p>因此,与此模式不同:</p>
<pre class="lang-py prettyprint-override"><code>f = open(...)
# do things with file
f.close()
</code></pre>
<p>您要执行以下操作:</p>
<pre class="lang-py prettyprint-override"><code>with open(...) as f:
# do things with file
</code></pre>