擅长:python、mysql、java
<p>第一步打开文件</p>
<pre><code> file = open("somefile.txt")
</code></pre>
<p>第二步去接电话</p>
^{pr2}$
<p>第3步使用列表理解</p>
<pre><code> new_lines = ["chr"+line for line in lines]
</code></pre>
<p>步骤4将新行写回文件</p>
<pre><code> with open("somefile.txt","w") as f:
f.writelines(new_lines)
</code></pre>
<p>为了不在内存中存储所有行</p>
<pre><code> file1 = open("some.txt")
file2 = open("output.txt","w")
for line in file1:
print >> file2, "chr"+ line
file1.close()
file2.close()
</code></pre>
<p>然后只需将<code>output.txt</code>复制到原始文件名</p>