blocks|key|2039500|text|这是因为在Python3中，字符串是unicode，因此默认情况下UNICODE标志是有意义的。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|2039501|Python+3：|2039502|>>>+a+=+re.compile("a")
>>>+a.flags
32
>>>+[k+for+k+in+dir(re)+if+getattr(re,+k)+==+32]
['U',+'UNICODE']|code-block|syntax|javascript|2039503|entityMap|0|LINK|mutability|MUTABLE|url|http://docs.python.org/2/library/re.html#re.UNICODE^0|X|7|X|7|0|0|0|0^^$0|@$1|2|3|4|5|6|7|U|8|@$9|V|A|W|B|C]]|D|@$9|X|A|Y|1|Z]]|E|$]]|$1|F|3|G|5|6|7|10|8|@]|D|@]|E|$]]|$1|H|3|I|5|J|7|11|8|@]|D|@]|E|$K|L]]|$1|M|3|-4|5|6|7|12|8|@]|D|@]|E|$]]]|N|$O|$5|P|Q|R|E|$S|T]]]]

It's because in Python 3, strings are unicode, and so it makes sense for the <a href="http://docs.python.org/2/library/re.html#re.UNICODE" rel="nofollow"><code>UNICODE</code></a> flag to be on by default.

Python 3:

<pre><code>&gt;&gt;&gt; a = re.compile("a")
&gt;&gt;&gt; a.flags
32
&gt;&gt;&gt; [k for k in dir(re) if getattr(re, k) == 32]
['U', 'UNICODE']
</code></pre>

blocks|key|3631572|text|在深入研究了re源代码之后，我在“sre_parse.py”中找到了以下内容：|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|3631573|def+fix_flags(src,+flags):
++++#+Check+and+fix+flags+according+to+the+type+of+pattern+(str+or+bytes)
++++if+isinstance(src,+str):
++++++++if+not+flags+&+SRE_FLAG_ASCII:
++++++++++++flags+%7C=+SRE_FLAG_UNICODE+#+<=====+LOOK+AT+THIS+LINE!!!!!
++++++++elif+flags+&+SRE_FLAG_UNICODE:
++++++++++++raise+ValueError("ASCII+and+UNICODE+flags+are+incompatible")
++++else:
++++++++if+flags+&+SRE_FLAG_UNICODE:
++++++++++++raise+ValueError("can't+use+UNICODE+flag+with+a+bytes+pattern")
++++return+flags|code-block|syntax|javascript|3631574|如果未添加"UNICODE“标志，则为您添加。它的值是SRE_FLAG_UNICODE+==+32，所以是2+%7C+32+==+re.IGNORECASE+%7C+re.UNICODE+==+34。|3631575|这个函数在python2.x的实现中不存在。|3631576|entityMap^0|6|2|0|0|R|M|1H|16|0|0^^$0|@$1|2|3|4|5|6|7|Q|8|@$9|R|A|S|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|T|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|U|8|@$9|V|A|W|B|C]|$9|X|A|Y|B|C]]|D|@]|E|$]]|$1|M|3|N|5|6|7|Z|8|@]|D|@]|E|$]]|$1|O|3|-4|5|6|7|10|8|@]|D|@]|E|$]]]|P|$]]

After digging through the <code>re</code> source code, I found the following in "sre_parse.py":

<pre><code>def fix_flags(src, flags):
 # Check and fix flags according to the type of pattern (str or bytes)
 if isinstance(src, str):
 if not flags &amp; SRE_FLAG_ASCII:
 flags |= SRE_FLAG_UNICODE # &lt;===== LOOK AT THIS LINE!!!!!
 elif flags &amp; SRE_FLAG_UNICODE:
 raise ValueError("ASCII and UNICODE flags are incompatible")
 else:
 if flags &amp; SRE_FLAG_UNICODE:
 raise ValueError("can't use UNICODE flag with a bytes pattern")
 return flags
</code></pre>

If the "UNICODE" flag is not added, it is added for you. It's value is <code>SRE_FLAG_UNICODE == 32</code>, so <code>2 | 32 == re.IGNORECASE | re.UNICODE == 34</code>.

This function does not exist in python2.x's implementation.

blocks|key|3659648|text|下面是Python3.x中的RegEx标志。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|3659649|import+re
print+(re.IGNORECASE)
print+(re.LOCALE)
print+(re.MULTILINE)
print+(re.DOTALL)
print+(re.UNICODE)
print+(re.VERBOSE)
print+(re.DEBUG)
print+(re.A)|code-block|syntax|javascript|3659650|输出|offset|length|style|BOLD|3659651|2
4
8
16
32
64
128
256|3659652|从docs，|CODE|3659653|字符串是Unicode代码点的不可变序列。
|blockquote|3659654|3659655|因此，默认情况下启用了re.UNICODE标志。既然您已经启用了re.IGNORECASE，那就是带有re.UNICODE的ORed，这就给了您34。|3659656|entityMap|0|LINK|mutability|MUTABLE|url|http://docs.python.org/3/library/stdtypes.html#text-sequence-type-str^0|0|0|0|2|0|0|1|4|1|4|0|0|0|0|B|A|W|D|1F|A|20|2|0^^$0|@$1|2|3|4|5|6|7|15|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|16|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|17|8|@$I|18|J|19|K|L]]|9|@]|A|$]]|$1|M|3|N|5|D|7|1A|8|@]|9|@]|A|$E|F]]|$1|O|3|P|5|6|7|1B|8|@$I|1C|J|1D|K|Q]]|9|@$I|1E|J|1F|1|1G]]|A|$]]|$1|R|3|S|5|T|7|1H|8|@]|9|@]|A|$]]|$1|U|3|-4|5|6|7|1I|8|@]|9|@]|A|$]]|$1|V|3|W|5|6|7|1J|8|@$I|1K|J|1L|K|Q]|$I|1M|J|1N|K|Q]|$I|1O|J|1P|K|Q]|$I|1Q|J|1R|K|Q]]|9|@]|A|$]]|$1|X|3|-4|5|6|7|1S|8|@]|9|@]|A|$]]]|Y|$Z|$5|10|11|12|A|$13|14]]]]

Following are the RegEx flags, in Python 3.x.

<pre><code>import re
print (re.IGNORECASE)
print (re.LOCALE)
print (re.MULTILINE)
print (re.DOTALL)
print (re.UNICODE)
print (re.VERBOSE)
print (re.DEBUG)
print (re.A)
</code></pre>

Output

<pre><code>2
4
8
16
32
64
128
256
</code></pre>

From the <a href="http://docs.python.org/3/library/stdtypes.html#text-sequence-type-str" rel="noreferrer"><code>docs</code></a>,

<blockquote>
 Strings are immutable sequences of Unicode code points.
</blockquote>

So, <code>re.UNICODE</code> flag is enabled by default. Since you have enabled <code>re.IGNORECASE</code>, that is ORed with <code>re.UNICODE</code> and that gives you <code>34</code>.

I am running my unit test suit with Python 3 on code that was developed under Python 2. All unit tests passed under Python 2 but not for Python 3. It seems there is some change in the implementation of <code>re</code>, and it is a real head scratcher for me. Below is a minimal working example to replicate my problem:

<pre><code>Python 2.7.6 (default, Dec 10 2013, 20:01:46) 
&gt;&gt;&gt; import re
&gt;&gt;&gt; a = re.compile('test', re.IGNORECASE)
&gt;&gt;&gt; assert a.flags == re.IGNORECASE
&gt;&gt;&gt; # No output, i.e. assertion passed
&gt;&gt;&gt; a.flags
2
&gt;&gt;&gt; re.IGNORECASE
2
</code></pre>

<hr>

<pre><code>Python 3.3.3 (default, Dec 10 2013, 20:13:18)
&gt;&gt;&gt; import re
&gt;&gt;&gt; a = re.compile('test', re.IGNORECASE)
&gt;&gt;&gt; assert a.flags == re.IGNORECASE
Traceback (most recent call last):
 File "&lt;stdin&gt;", line 1, in &lt;module&gt;
AssertionError
&gt;&gt;&gt; a.flags
34
&gt;&gt;&gt; re.IGNORECASE
2
</code></pre>

<hr>

Clearly something is going on that I don't expect! I am assuming that there is some set of default flags that are OR'd together to make <code>flags</code> be 34 in python3. What I want to know is what these are so that I can make my assertion pass by comparing against the proper flags. As a bonus, what is the purpose for this?

Changes in re module between Python 2 and Python 3

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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我正在用Python3在Python 2下开发的代码上运行我的单元测试套装。所有的单元测试都是在Python2下通过的，但对于Python3却没有。re的实现似乎有了一些变化，这对我来说真是太麻烦了。下面是一个复制我的问题的最小的工作示例：Python 2.7.6 (default, Dec 10 2013, 20:0...

问Python 2和Python 3之间re模块的更改
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