blocks|key|1306637|text|也许在text+=+re.sub('foobar',+'bar',+text)之后关闭文件，重新打开它以进行写入(从而清除旧内容)，并将更新的文本写入其中，可能会更容易、更整洁。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1306638|entityMap^0|3|10|0^^$0|@$1|2|3|4|5|6|7|H|8|@$9|I|A|J|B|C]]|D|@]|E|$]]|$1|F|3|-4|5|6|7|K|8|@]|D|@]|E|$]]]|G|$]]

Probably it would be easier and neater to close the file after <code>text = re.sub('foobar', 'bar', text)</code>, re-open it for writing (thus clearing old contents), and write your updated text to it.

blocks|key|1306693|text|fileinput模块有一个inplace模式，用于在不使用临时文件等的情况下将更改写入到正在处理的文件中。该模块很好地封装了循环遍历文件列表中的行的常见操作，通过一个对象来透明地跟踪文件名、行号等，如果你想在循环中检查它们的话。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1306694|from+fileinput+import+FileInput
for+line+in+FileInput("file",+inplace=1):
++++line+=+line.replace("foobar",+"bar")
++++print(line)|code-block|syntax|javascript|1306695|entityMap|0|LINK|mutability|MUTABLE|url|https://docs.python.org/2/library/fileinput.html^0|0|9|E|7|0|9|0|0|0^^$0|@$1|2|3|4|5|6|7|S|8|@$9|T|A|U|B|C]|$9|V|A|W|B|C]]|D|@$9|X|A|Y|1|Z]]|E|$]]|$1|F|3|G|5|H|7|10|8|@]|D|@]|E|$I|J]]|$1|K|3|-4|5|6|7|11|8|@]|D|@]|E|$]]]|L|$M|$5|N|O|P|E|$Q|R]]]]

The <a href="https://docs.python.org/2/library/fileinput.html" rel="noreferrer"><code>fileinput</code></a> module has an <code>inplace</code> mode for writing changes to the file you are processing without using temporary files etc. The module nicely encapsulates the common operation of looping over the lines in a list of files, via an object which transparently keeps track of the file name, line number etc if you should want to inspect them inside the loop.
<pre><code>from fileinput import FileInput
for line in FileInput(&quot;file&quot;, inplace=1):
 line = line.replace(&quot;foobar&quot;, &quot;bar&quot;)
 print(line)
</code></pre>

blocks|key|1306739|text|如果您不想关闭和重新打开该文件，以避免争用条件，您可以对其执行truncate：|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1306740|f+=+open(filename,+'r%2B')
text+=+f.read()
text+=+re.sub('foobar',+'bar',+text)
f.seek(0)
f.write(text)
f.truncate()
f.close()|code-block|syntax|javascript|1306741|使用open作为上下文管理器的功能也可能是cleaner+and+safer的，这将关闭文件处理程序，即使发生错误也是如此！|1306742|with+open(filename,+'r%2B')+as+f:
++++text+=+f.read()
++++text+=+re.sub('foobar',+'bar',+text)
++++f.seek(0)
++++f.write(text)
++++f.truncate()|1306743|entityMap|0|LINK|mutability|MUTABLE|url|https://docs.python.org/3/library/io.html#io.IOBase.truncate|1|https://stackoverflow.com/a/3644618/4541045^0|V|8|V|8|0|0|0|2|4|L|H|1|0|0^^$0|@$1|2|3|4|5|6|7|Y|8|@$9|Z|A|10|B|C]]|D|@$9|11|A|12|1|13]]|E|$]]|$1|F|3|G|5|H|7|14|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|15|8|@$9|16|A|17|B|C]]|D|@$9|18|A|19|1|1A]]|E|$]]|$1|M|3|N|5|H|7|1B|8|@]|D|@]|E|$I|J]]|$1|O|3|-4|5|6|7|1C|8|@]|D|@]|E|$]]]|P|$Q|$5|R|S|T|E|$U|V]]|W|$5|R|S|T|E|$U|X]]]]

If you don't want to close and reopen the file, to avoid race conditions, you could <a href="https://docs.python.org/3/library/io.html#io.IOBase.truncate" rel="noreferrer"><code>truncate</code></a> it:
<pre><code>f = open(filename, 'r+')
text = f.read()
text = re.sub('foobar', 'bar', text)
f.seek(0)
f.write(text)
f.truncate()
f.close()
</code></pre>
The functionality will likely also be <a href="https://stackoverflow.com/a/3644618/4541045">cleaner and safer</a> using <code>open</code> as a context manager, which will close the file handler, even if an error occurs!
<pre><code>with open(filename, 'r+') as f:
 text = f.read()
 text = re.sub('foobar', 'bar', text)
 f.seek(0)
 f.write(text)
 f.truncate()
</code></pre>

blocks|key|1306777|text|尝试将其写入到新文件中。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1306778|f+=+open(filename,+'r%2B')
f2=+open(filename2,'a%2B')
text+=+f.read()
text+=+re.sub('foobar',+'bar',+text)
f.seek(0)
f.close()
f2.write(text)
fw.close()|code-block|syntax|javascript|1306779|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

Try writing it in a new file..

<pre><code>f = open(filename, 'r+')
f2= open(filename2,'a+')
text = f.read()
text = re.sub('foobar', 'bar', text)
f.seek(0)
f.close()
f2.write(text)
fw.close()
</code></pre>

blocks|key|1306800|text|老实说，你可以看看我构建的这个类，它执行基本的文件操作。write方法覆盖并追加保留旧数据。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1306801|class+IO:
++++def+read(self,+filename):
++++++++toRead+=+open(filename,+"rb")

++++++++out+=+toRead.read()
++++++++toRead.close()
++++++++
++++++++return+out
++++
++++def+write(self,+filename,+data):
++++++++toWrite+=+open(filename,+"wb")

++++++++out+=+toWrite.write(data)
++++++++toWrite.close()

++++def+append(self,+filename,+data):
++++++++append+=+self.read(filename)
++++++++self.write(filename,+append%2Bdata)|code-block|syntax|javascript|1306802|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

Honestly you can take a look at this class that I built which does basic file operations. The write method overwrites and append keeps old data.
<pre><code>class IO:
 def read(self, filename):
 toRead = open(filename, &quot;rb&quot;)

 out = toRead.read()
 toRead.close()
 
 return out
 
 def write(self, filename, data):
 toWrite = open(filename, &quot;wb&quot;)

 out = toWrite.write(data)
 toWrite.close()

 def append(self, filename, data):
 append = self.read(filename)
 self.write(filename, append+data)
 
</code></pre>

blocks|key|1091695|text|我发现先读后写会更容易记住。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1091696|例如：|1091697|with+open('file')+as+f:
++++data+=+f.read()
with+open('file',+'w')+as+f:
++++f.write('hello')|code-block|syntax|javascript|1091698|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|K|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|L|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|M|8|@]|9|@]|A|$G|H]]|$1|I|3|-4|5|6|7|N|8|@]|9|@]|A|$]]]|J|$]]

I find it easier to remember to just read it and then write it.
For example:
<pre class="lang-py prettyprint-override"><code>with open('file') as f:
 data = f.read()
with open('file', 'w') as f:
 f.write('hello')
</code></pre>

blocks|key|1306879|text|对于任何想要逐行阅读和覆盖的人，请参考此答案。https://stackoverflow.com/a/71285415/11442980|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|1306880|filename+=+input("Enter+filename:+")
with+open(filename,+'r%2B')+as+file:
++++lines+=+file.readlines()
++++file.seek(0)
++++for+line+in+lines:
++++++++value+=+int(line)
++++++++file.write(str(value+%2B+1))
++++file.truncate()|code-block|syntax|javascript|1306881|entityMap|0|LINK|mutability|MUTABLE|url|https://stackoverflow.com/a/71285415/11442980^0|N|19|0|0|0^^$0|@$1|2|3|4|5|6|7|Q|8|@]|9|@$A|R|B|S|1|T]]|C|$]]|$1|D|3|E|5|F|7|U|8|@]|9|@]|C|$G|H]]|$1|I|3|-4|5|6|7|V|8|@]|9|@]|C|$]]]|J|$K|$5|L|M|N|C|$O|P]]]]

To anyone who wants to read and overwrite by line, refer to this answer.
<a href="https://stackoverflow.com/a/71285415/11442980">https://stackoverflow.com/a/71285415/11442980</a>
<pre><code>filename = input(&quot;Enter filename: &quot;)
with open(filename, 'r+') as file:
 lines = file.readlines()
 file.seek(0)
 for line in lines:
 value = int(line)
 file.write(str(value + 1))
 file.truncate()
</code></pre>

Currently I'm using this:

<pre><code>f = open(filename, 'r+')
text = f.read()
text = re.sub('foobar', 'bar', text)
f.seek(0)
f.write(text)
f.close()
</code></pre>

But the problem is that the old file is larger than the new file. So I end up with a new file that has a part of the old file on the end of it.

Read and overwrite a file in Python

目前我使用的是：f = open(filename, 'r+')text = f.read()text = re.sub('foobar', 'bar', text)f.seek(0)f.write(text)f.close()但问题是旧文件比新文件大。所以我最终得到了一个新文件，在它的末尾有旧文件的一部分。

问在Python中读取和覆盖文件
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