擅长:python、mysql、java
<p>一个简单的解决方案是覆盖整个文件,而不是就地修改:</p>
<pre><code>with open("file.txt") as input:
# Read non-empty lines from input file
lines = [line for line in input if line.strip()]
with open("file.txt", "w") as output:
for line in lines:
output.write(line)
output.write("orange\n")
</code></pre>
<p>只要文件不太大,此代码就可以正常工作。</p>
<p>您可以通过打开文件进行读写、在文件末尾查找换行符的数量、查找到第一个尾随换行符之后的位置并将该行写入该位置来更有效地执行此操作。这更有效,但也需要更详细的代码,所以我只会在简单的解决方案不够快的情况下这样做。</p>
<p><strong>编辑</strong>:以下是我对更有效的方法的看法:</p>
<pre><code>with open("file.txt", "r+U") as f:
try:
f.seek(-1, 2)
while f.read(1) == "\n":
f.seek(-2, 1) # go back two characters, since
# reading advances by one character
except IOError: # seek failed, so the file consists
f.seek(0) # exclusively of newline characters
else:
f.write("\n") # Add exactly one newline character
f.write("orange\n") # Add a new line
</code></pre>
<p>这对于任意数量的尾随换行符都是正确的,包括一个或两个以上的换行符。</p>