blocks|key|1597098|text|当您需要打开具有特定编码的文件时，可以使用codecs模块。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1597099|entityMap^0|L|6|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|$]]

When you need to open a file that has a certain encoding, you would use the <code>codecs</code> module.

blocks|key|1597115|text|当您正在处理文本文件并希望将其透明地编码和解码为Unicode对象时。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1597116|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|D|8|@]|9|@]|A|$]]|$1|B|3|-4|5|6|7|E|8|@]|9|@]|A|$]]]|C|$]]

When you're working with text files and want transparent encoding and decoding into Unicode objects.

blocks|key|1952042|text|就我个人而言，除非明确需要使用open**，否则我总是使用codecs.open。原因是有太多次我被utf-8输入偷偷地放入我的程序中。“哦，我只知道它永远是ascii”，这是一个经常被打破的假设。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1952043|根据我的经验，假设'utf-8‘作为默认编码往往是一个更安全的默认选择，因为ASCII可以被视为UTF-8，但反之亦然。在这些情况下，当我确实知道输入是ASCII码时，我仍然会使用codecs.open，因为我是"explicit+is+better+than+implicit"的坚定支持者。|1952044|**+-在Python2.x中，正如Python3中的问题注释所述，open取代了codecs.open|1952045|entityMap|0|LINK|mutability|MUTABLE|url|http://www.python.org/dev/peps/pep-0020/^0|F|4|T|B|0|2I|B|2Y|Y|0|0|Y|4|15|B|0^^$0|@$1|2|3|4|5|6|7|R|8|@$9|S|A|T|B|C]|$9|U|A|V|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|W|8|@$9|X|A|Y|B|C]]|D|@$9|Z|A|10|1|11]]|E|$]]|$1|H|3|I|5|6|7|12|8|@$9|13|A|14|B|C]|$9|15|A|16|B|C]]|D|@]|E|$]]|$1|J|3|-4|5|6|7|17|8|@]|D|@]|E|$]]]|K|$L|$5|M|N|O|E|$P|Q]]]]

Personally, I always use <code>codecs.open</code> unless there's a clear identified need to use <code>open</code>**. The reason is that there's been so many times when I've been bitten by having utf-8 input sneak into my programs. "Oh, I just know it'll always be ascii" tends to be an assumption that gets broken often.

Assuming 'utf-8' as the default encoding tends to be a safer default choice in my experience, since ASCII can be treated as UTF-8, but the converse is not true. And in those cases when I truly do know that the input is ASCII, then I still do <code>codecs.open</code> as I'm a firm believer in <a href="http://www.python.org/dev/peps/pep-0020/" rel="noreferrer">"explicit is better than implicit"</a>.

** - in Python 2.x, as the comment on the question states in Python 3 <code>open</code> replaces <code>codecs.open</code>

blocks|key|5481225|text|在Python+2中，有unicode字符串和字节字符串。如果你只使用字节串，你可以读/写一个用open()打开的文件。毕竟，字符串只是字节。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|5481226|比方说，当您有一个unicode字符串并执行以下操作时，问题就出现了：|5481227|>>>+example+=+u'Μου+αρέσει+Ελληνικά'
>>>+open('sample.txt',+'w').write(example)
Traceback+(most+recent+call+last):
File+"<stdin>",+line+1,+in+<module>
UnicodeEncodeError:+'ascii'+codec+can't+encode+characters+in+position+0-2:+ordinal+not+in+range(128)|code-block|syntax|javascript|5481228|显然，在这里，您要么显式地以utf-8对unicode字符串进行编码，要么使用codecs.open透明地为您完成此操作。|5481229|如果你只使用字节串，那么没问题：|5481230|>>>+example+=+'Μου+αρέσει+Ελληνικά'
>>>+open('sample.txt',+'w').write(example)
>>>|5481231|它比这复杂得多，因为当您将unicode和bytestring字符串与%2B操作符连接在一起时，您会得到一个unicode字符串。很容易被它咬到。|5481232|此外，codecs.open不喜欢传入非ASCII字符的字节串：|5481233|codecs.open('test',+'w',+encoding='utf-8').write('Μου+αρέσει')
Traceback+(most+recent+call+last):
++File+"<stdin>",+line+1,+in+<module>
++File+"/usr/lib/python2.7/codecs.py",+line+691,+in+write
++++return+self.writer.write(data)
++File+"/usr/lib/python2.7/codecs.py",+line+351,+in+write
++++data,+consumed+=+self.encode(object,+self.errors)
UnicodeDecodeError:+'ascii'+codec+can't+decode+byte+0xce+in+position+0:+ordinal+not+in+range(128)|5481234|关于输入/输出字符串的建议通常是“尽早转换为unicode，并尽可能晚地转换回字节字符串”。使用codecs.open可以非常容易地完成后一项工作。|5481235|只是要小心，你给它的是unicode字符串，而不是可能包含非ASCII字符的字节字符串。|5481236|entityMap^0|1C|6|0|0|0|13|B|0|0|0|Z|1|0|3|B|0|0|1C|B|0|0^^$0|@$1|2|3|4|5|6|7|14|8|@$9|15|A|16|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|17|8|@]|D|@]|E|$]]|$1|H|3|I|5|J|7|18|8|@]|D|@]|E|$K|L]]|$1|M|3|N|5|6|7|19|8|@$9|1A|A|1B|B|C]]|D|@]|E|$]]|$1|O|3|P|5|6|7|1C|8|@]|D|@]|E|$]]|$1|Q|3|R|5|J|7|1D|8|@]|D|@]|E|$K|L]]|$1|S|3|T|5|6|7|1E|8|@$9|1F|A|1G|B|C]]|D|@]|E|$]]|$1|U|3|V|5|6|7|1H|8|@$9|1I|A|1J|B|C]]|D|@]|E|$]]|$1|W|3|X|5|J|7|1K|8|@]|D|@]|E|$K|L]]|$1|Y|3|Z|5|6|7|1L|8|@$9|1M|A|1N|B|C]]|D|@]|E|$]]|$1|10|3|11|5|6|7|1O|8|@]|D|@]|E|$]]|$1|12|3|-4|5|6|7|1P|8|@]|D|@]|E|$]]]|13|$]]

In Python 2 there are unicode strings and bytestrings. If you just use bytestrings, you can read/write to a file opened with <code>open()</code> just fine. After all, the strings are just bytes. 

The problem comes when, say, you have a unicode string and you do the following:

<pre><code>&gt;&gt;&gt; example = u'Μου αρέσει Ελληνικά'
&gt;&gt;&gt; open('sample.txt', 'w').write(example)
Traceback (most recent call last):
File "&lt;stdin&gt;", line 1, in &lt;module&gt;
UnicodeEncodeError: 'ascii' codec can't encode characters in position 0-2: ordinal not in range(128)
</code></pre>

So here obviously you either explicitly encode your unicode string in utf-8 or you use <code>codecs.open</code> to do it for you transparently. 

If you're only ever using bytestrings then no problems:

<pre><code>&gt;&gt;&gt; example = 'Μου αρέσει Ελληνικά'
&gt;&gt;&gt; open('sample.txt', 'w').write(example)
&gt;&gt;&gt;
</code></pre>

It gets more involved than this because when you concatenate a unicode and bytestring string with the <code>+</code> operator you get a unicode string. Easy to get bitten by that one.

Also <code>codecs.open</code> doesn't like bytestrings with non-ASCII chars being passed in:

<pre><code>codecs.open('test', 'w', encoding='utf-8').write('Μου αρέσει')
Traceback (most recent call last):
 File "&lt;stdin&gt;", line 1, in &lt;module&gt;
 File "/usr/lib/python2.7/codecs.py", line 691, in write
 return self.writer.write(data)
 File "/usr/lib/python2.7/codecs.py", line 351, in write
 data, consumed = self.encode(object, self.errors)
UnicodeDecodeError: 'ascii' codec can't decode byte 0xce in position 0: ordinal not in range(128)
</code></pre>

The advice about strings for input/ouput is normally "convert to unicode as early as possible and back to bytestrings as late as possible". Using <code>codecs.open</code> allows you to do the latter very easily.

Just be careful that you are giving it unicode strings and not bytestrings that may have non-ASCII characters.

blocks|key|4062806|text|从Python2.6开始，一个好的做法是使用io.open()，它也接受一个encoding参数，就像现在已经过时的codecs.open()一样。在Python3中，io.open是内置open()的别名。因此，io.open()可以在Python2.6和所有更高版本中工作，包括Python3.4。请参阅文档：http://docs.python.org/3.4/library/io.html|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|4062807|现在，对于原始问题:当在Python2中读取text+(包括“纯文本”，超文本标记语言，XML和JSON)时，你应该始终使用显式编码的io.open()，或者在Python3中使用显式编码的open()。这样做意味着你可以正确地解码Unicode，或者马上就会出错，这使得调试变得更加容易。|BOLD|4062808|纯ASCII“纯文本”是一个来自遥远过去的神话。正确的英文文本使用大引号、破折号、项目符号、欧元(欧元符号)，甚至分隔符(¨)。别天真了！(我们不要忘记Façade设计模式！)|4062809|因为纯ASCII不是真正的选项，没有显式编码的open()是，对于读取二进制文件很有用。|4062810|entityMap|0|LINK|mutability|MUTABLE|url|http://docs.python.org/3.4/library/io.html^0|M|9|12|8|1M|D|2C|7|2M|6|2Z|9|4D|16|0|0|M|4|1V|9|2N|6|0|0|N|6|Z|3|0^^$0|@$1|2|3|4|5|6|7|U|8|@$9|V|A|W|B|C]|$9|X|A|Y|B|C]|$9|Z|A|10|B|C]|$9|11|A|12|B|C]|$9|13|A|14|B|C]|$9|15|A|16|B|C]]|D|@$9|17|A|18|1|19]]|E|$]]|$1|F|3|G|5|6|7|1A|8|@$9|1B|A|1C|B|H]|$9|1D|A|1E|B|C]|$9|1F|A|1G|B|C]]|D|@]|E|$]]|$1|I|3|J|5|6|7|1H|8|@]|D|@]|E|$]]|$1|K|3|L|5|6|7|1I|8|@$9|1J|A|1K|B|C]|$9|1L|A|1M|B|H]]|D|@]|E|$]]|$1|M|3|-4|5|6|7|1N|8|@]|D|@]|E|$]]]|N|$O|$5|P|Q|R|E|$S|T]]]]

Since Python 2.6, a good practice is to use <code>io.open()</code>, which also takes an <code>encoding</code> argument, like the now obsolete <code>codecs.open()</code>. In Python 3, <code>io.open</code> is an alias for the <code>open()</code> built-in. So <code>io.open()</code> works in Python 2.6 and all later versions, including Python 3.4. See docs: <a href="http://docs.python.org/3.4/library/io.html" rel="noreferrer">http://docs.python.org/3.4/library/io.html</a>

Now, for the original question: when reading text (including "plain text", HTML, XML and JSON) in Python 2 you should always use <code>io.open()</code> with an explicit encoding, or <code>open()</code> with an explicit encoding in Python 3. Doing so means you get correctly decoded Unicode, or get an error right off the bat, making it much easier to debug.

Pure ASCII "plain text" is a myth from the distant past. Proper English text uses curly quotes, em-dashes, bullets, € (euro signs) and even diaeresis (¨). Don't be naïve! (And let's not forget the Façade design pattern!) 

Because pure ASCII is not a real option, <code>open()</code> without an explicit encoding is only useful to read binary files.

blocks|key|1952228|text|要加载二进制文件时，请使用f+=+io.open(filename,+'b').|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1952229|For打开文本文件，并始终使用具有显式编码的|unordered-list-item|1952230|。|1952231|1952232|1952233|然而，在、Python3、中，open与io.open做同样的事情，也可以使用它。|BOLD|1952234|1952235|+注意：+codecs.open计划成为deprecated，并在Python2.6中引入后被io.open取代。只有当代码需要与早期的python版本兼容时，我才会使用它。有关python中的编解码器和unicode的更多信息，请参阅Unicode+HOWTO。|blockquote|1952236|1952237|entityMap|0|LINK|mutability|MUTABLE|url|https://bugs.python.org/issue8796|1|https://docs.python.org/2/library/io.html#io.open|2|https://docs.python.org/2/howto/unicode.html^0|D|Q|0|0|0|0|0|4|9|F|4|K|7|0|0|1|3|X|9|5|B|1B|7|K|A|0|1B|7|1|3A|D|2|0|0^^$0|@$1|2|3|4|5|6|7|16|8|@$9|17|A|18|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|19|8|@]|D|@]|E|$]]|$1|I|3|J|5|H|7|1A|8|@]|D|@]|E|$]]|$1|K|3|-4|5|6|7|1B|8|@]|D|@]|E|$]]|$1|L|3|-4|5|6|7|1C|8|@]|D|@]|E|$]]|$1|M|3|N|5|6|7|1D|8|@$9|1E|A|1F|B|O]|$9|1G|A|1H|B|C]|$9|1I|A|1J|B|C]]|D|@]|E|$]]|$1|P|3|-4|5|6|7|1K|8|@]|D|@]|E|$]]|$1|Q|3|R|5|S|7|1L|8|@$9|1M|A|1N|B|O]|$9|1O|A|1P|B|O]|$9|1Q|A|1R|B|C]|$9|1S|A|1T|B|C]]|D|@$9|1U|A|1V|1|1W]|$9|1X|A|1Y|1|1Z]|$9|20|A|21|1|22]]|E|$]]|$1|T|3|-4|5|6|7|23|8|@]|D|@]|E|$]]|$1|U|3|-4|5|6|7|24|8|@]|D|@]|E|$]]]|V|$W|$5|X|Y|Z|E|$10|11]]|12|$5|X|Y|Z|E|$10|13]]|14|$5|X|Y|Z|E|$10|15]]]]

<ul>
<li>When you want to load a binary file, use
<code>f = io.open(filename, 'b')</code>.</li>
<li>For opening a text file, always use <code>f = io.open(filename, encoding='utf-8')</code> with explicit encoding.</li>
</ul>

In python 3 however <code>open</code> does the same thing as <code>io.open</code> and can be used instead.

<blockquote>
 Note: <code>codecs.open</code> is planned to become <a href="https://bugs.python.org/issue8796" rel="nofollow noreferrer">deprecated</a> and replaced by <a href="https://docs.python.org/2/library/io.html#io.open" rel="nofollow noreferrer"><code>io.open</code></a> after its introduction in python 2.6. I would only use it if code needs to be compatible with earlier python versions. For more information on codecs and unicode in python see the <a href="https://docs.python.org/2/howto/unicode.html" rel="nofollow noreferrer">Unicode HOWTO</a>.
</blockquote>

blocks|key|1952284|text|我想，codecs.open只是Python+2时代的残余，当时内置的开放具有更简单的界面和更少的功能。在Python2中，内置的open不接受编码参数，所以如果您想使用二进制模式或默认编码之外的其他方式，则应该使用codecs.open。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1952285|在Python+2.6中，io模块提供了帮助，使事情变得更简单。根据官方documentation|1952286|New+in+version+2.6.

The+io+module+provides+the+Python+interfaces+to+stream+handling.
Under+Python+2.x,+this+is+proposed+as+an+alternative+to+the
built-in+file+object,+but+in+Python+3.x+it+is+the+default
interface+to+access+files+and+streams.|code-block|syntax|javascript|1952287|话虽如此，在目前的场景中，我能想到的codecs.open的唯一用途就是向后兼容。在所有其他场景中(除非您使用的是Python2.6版)，最好使用io.open。在Python+3.x中，io.open与built-in+open相同|1952288|备注：|BOLD|1952289|codecs.open和io.open在语法上也有区别。|1952290|codecs.open|1952291|open(filename,+mode='rb',+encoding=None,+errors='strict',+buffering=1)|1952292|io.open|1952293|open(file,+mode='r',+buffering=-1,+encoding=None,
+++++errors=None,+newline=None,+closefd=True,+opener=None)|1952294|entityMap|0|LINK|mutability|MUTABLE|url|https://docs.python.org/2/library/io.html^0|3|B|G|8|1T|4|0|1|A|10|D|0|0|0|I|B|21|7|2A|A|2M|7|2U|D|0|0|3|0|0|B|C|7|0|0|B|0|0|0|7|0|0^^$0|@$1|2|3|4|5|6|7|19|8|@$9|1A|A|1B|B|C]|$9|1C|A|1D|B|C]|$9|1E|A|1F|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|1G|8|@$9|1H|A|1I|B|C]]|D|@$9|1J|A|1K|1|1L]]|E|$]]|$1|H|3|I|5|J|7|1M|8|@]|D|@]|E|$K|L]]|$1|M|3|N|5|6|7|1N|8|@$9|1O|A|1P|B|C]|$9|1Q|A|1R|B|C]|$9|1S|A|1T|B|C]|$9|1U|A|1V|B|C]|$9|1W|A|1X|B|C]]|D|@]|E|$]]|$1|O|3|P|5|6|7|1Y|8|@$9|1Z|A|20|B|Q]]|D|@]|E|$]]|$1|R|3|S|5|6|7|21|8|@$9|22|A|23|B|C]|$9|24|A|25|B|C]]|D|@]|E|$]]|$1|T|3|U|5|6|7|26|8|@$9|27|A|28|B|C]]|D|@]|E|$]]|$1|V|3|W|5|J|7|29|8|@]|D|@]|E|$K|L]]|$1|X|3|Y|5|6|7|2A|8|@$9|2B|A|2C|B|C]]|D|@]|E|$]]|$1|Z|3|10|5|J|7|2D|8|@]|D|@]|E|$K|L]]|$1|11|3|-4|5|6|7|2E|8|@]|D|@]|E|$]]]|12|$13|$5|14|15|16|E|$17|18]]]]

<code>codecs.open</code>, i suppose, is just a remnant from the <code>Python 2</code> days when the built-in open had a much simpler interface and fewer capabilities. In Python 2, built-in <code>open</code> doesn't take an encoding argument, so if you want to use something other than binary mode or the default encoding, codecs.open was supposed to be used.

In <code>Python 2.6</code>, the io module came to the aid to make things a bit simpler.
According to the official <a href="https://docs.python.org/2/library/io.html" rel="nofollow noreferrer">documentation</a>

<pre><code>New in version 2.6.

The io module provides the Python interfaces to stream handling.
Under Python 2.x, this is proposed as an alternative to the
built-in file object, but in Python 3.x it is the default
interface to access files and streams.
</code></pre>

Having said that, the only use i can think of <code>codecs.open</code> in the current scenario is for the backward compatibility. In all other scenarios (unless you are using Python &lt; 2.6) it is preferable to use <code>io.open</code>. Also in <code>Python 3.x</code> <code>io.open</code> is the same as <code>built-in open</code>

Note:

There is a syntactical difference between <code>codecs.open</code> and <code>io.open</code> as well.

<code>codecs.open</code>:

<pre><code>open(filename, mode='rb', encoding=None, errors='strict', buffering=1)
</code></pre>

<code>io.open</code>:

<pre><code>open(file, mode='r', buffering=-1, encoding=None,
 errors=None, newline=None, closefd=True, opener=None)
</code></pre>

There are two ways to open a text file in Python:

<pre><code>f = open(filename)
</code></pre>

And

<pre><code>import codecs
f = codecs.open(filename, encoding="utf-8")
</code></pre>

When is <code>codecs.open</code> preferable to <code>open</code>?

Difference between open and codecs.open in Python

翻译质量差，导致语言生硬或混乱。

没有提供实际的解决方法或示例。

解答不清晰，无法理解或解决问题。

页面排版不美观，阅读体验差。

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在Python中打开文本文件有两种方法：f = open(filename)和import codecsf = codecs.open(filename, encoding="utf-8")什么情况下codecs.open比open更可取

问Python语言中open和codecs.open的区别
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