blocks|key|789943|text|对于类XPath选择器的工作方式，还需要做更多的工作。'/'是一个有效的字典键，那么如何|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|789944|foo={'/':{'/':'eggs'},'//':'ham'}|code-block|syntax|javascript|789945|会被处理？|789946|foo.select("///")|789947|是模棱两可的。|789948|entityMap^0|R|3|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|S|8|@$9|T|A|U|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|V|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|W|8|@]|D|@]|E|$]]|$1|M|3|N|5|H|7|X|8|@]|D|@]|E|$I|J]]|$1|O|3|P|5|6|7|Y|8|@]|D|@]|E|$]]|$1|Q|3|-4|5|6|7|Z|8|@]|D|@]|E|$]]]|R|$]]

More work would have to be put into how the XPath-like selector would work.
<code>'/'</code> is a valid dictionary key, so how would 

<pre><code>foo={'/':{'/':'eggs'},'//':'ham'}
</code></pre>

be handled?

<pre><code>foo.select("///")
</code></pre>

would be ambiguous.

blocks|key|573741|text|你有什么理由像XPath模式那样查询它吗？正如你的问题的评论者所建议的，它只是一个字典，所以你可以以嵌套的方式访问元素。另外，考虑到数据是JSON格式的，您也可以使用simplejson模块来加载它并访问元素。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|573742|有一个项目JSONPATH，它试图帮助人们做与您打算做的相反的事情(给定一个XPATH，如何通过python对象轻松访问它)，这似乎更有用。|offset|length|573743|entityMap|0|LINK|mutability|MUTABLE|url|http://pypi.python.org/pypi/jsonpath^0|0|5|8|0|0^^$0|@$1|2|3|4|5|6|7|N|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|O|8|@]|9|@$D|P|E|Q|1|R]]|A|$]]|$1|F|3|-4|5|6|7|S|8|@]|9|@]|A|$]]]|G|$H|$5|I|J|K|A|$L|M]]]]

Is there any reason for you to the query it the way like the XPath pattern? As the commenter to your question suggested, it just a dictionary, so you can access the elements in a nest manner. Also, considering that data is in the form of JSON, you can use simplejson module to load it and access the elements too.

There is this project <a href="http://pypi.python.org/pypi/jsonpath" rel="nofollow">JSONPATH</a>, which is trying to help people do opposite of what you intend to do (given an XPATH, how to make it easily accessible via python objects), which seems more useful.

blocks|key|790018|text|不是很漂亮，但是你可以使用类似这样的东西|type|unstyled|depth|inlineStyleRanges|entityRanges|data|790019|def+xpath_get(mydict,+path):
++++elem+=+mydict
++++try:
++++++++for+x+in+path.strip("/").split("/"):
++++++++++++elem+=+elem.get(x)
++++except:
++++++++pass

++++return+elem|code-block|syntax|javascript|790020|当然，这不支持像索引这样的xpath内容。更不用说unutbu指出的/密钥陷阱了。|offset|length|style|CODE|790021|entityMap^0|0|0|Y|1|0^^$0|@$1|2|3|4|5|6|7|O|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|P|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|Q|8|@$I|R|J|S|K|L]]|9|@]|A|$]]|$1|M|3|-4|5|6|7|T|8|@]|9|@]|A|$]]]|N|$]]

Not exactly beautiful, but you might use sth like

<pre><code>def xpath_get(mydict, path):
 elem = mydict
 try:
 for x in path.strip("/").split("/"):
 elem = elem.get(x)
 except:
 pass

 return elem
</code></pre>

This doesn't support xpath stuff like indices, of course ... not to mention the <code>/</code> key trap unutbu indicated.

blocks|key|790078|text|另一种选择(除了jellybean建议的)是这样的：|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|790079|def+querydict(d,+q):
++keys+=+q.split('/')
++nd+=+d
++for+k+in+keys:
++++if+k+==+'':
++++++continue
++++if+k+in+nd:
++++++nd+=+nd[k]
++++else:
++++++return+None
++return+nd

foo+=+{
++'spam':'eggs',
++'morefoo':+{
+++++++++++++++'bar':'soap',
+++++++++++++++'morebar':+{'bacon'+:+'foobar'}
++++++++++++++}
+++}
print+querydict(foo,+"/morefoo/morebar")|code-block|syntax|javascript|790080|entityMap|0|LINK|mutability|MUTABLE|url|https://stackoverflow.com/questions/7320319/xpath-like-query-for-nested-python-dictionaries/7320664#7320664^0|8|9|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]]]]

Another alternative (besides that suggested by <a href="https://stackoverflow.com/questions/7320319/xpath-like-query-for-nested-python-dictionaries/7320664#7320664">jellybean</a>) is this:

<pre><code>def querydict(d, q):
 keys = q.split('/')
 nd = d
 for k in keys:
 if k == '':
 continue
 if k in nd:
 nd = nd[k]
 else:
 return None
 return nd

foo = {
 'spam':'eggs',
 'morefoo': {
 'bar':'soap',
 'morebar': {'bacon' : 'foobar'}
 }
 }
print querydict(foo, "/morefoo/morebar")
</code></pre>

blocks|key|573878|text|现在有一种更简单的方法可以做到这一点。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|573879|http://github.com/akesterson/dpath-python|offset|length|573880|$+easy_install+dpath
>>>+dpath.util.search(YOUR_DICTIONARY,+"morefoo/morebar")|code-block|syntax|javascript|573881|..。好了。或者，如果您不喜欢在视图(保留路径的合并字典)中返回结果，则改为生成它们：|573882|$+easy_install+dpath
>>>+for+(path,+value)+in+dpath.util.search(YOUR_DICTIONARY,+"morefoo/morebar",+yielded=True)|573883|..。完成了。在这种情况下，‘'value’将包含{'bacon'：'foobar'}。|573884|entityMap|0|LINK|mutability|MUTABLE|url^0|0|0|15|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|X|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|Y|8|@]|9|@$D|Z|E|10|1|11]]|A|$]]|$1|F|3|G|5|H|7|12|8|@]|9|@]|A|$I|J]]|$1|K|3|L|5|6|7|13|8|@]|9|@]|A|$]]|$1|M|3|N|5|H|7|14|8|@]|9|@]|A|$I|J]]|$1|O|3|P|5|6|7|15|8|@]|9|@]|A|$]]|$1|Q|3|-4|5|6|7|16|8|@]|9|@]|A|$]]]|R|$S|$5|T|U|V|A|$W|C]]]]

There is an easier way to do this now.

<a href="http://github.com/akesterson/dpath-python">http://github.com/akesterson/dpath-python</a>

<pre><code>$ easy_install dpath
&gt;&gt;&gt; dpath.util.search(YOUR_DICTIONARY, "morefoo/morebar")
</code></pre>

... done. Or if you don't like getting your results back in a view (merged dictionary that retains the paths), yield them instead:

<pre><code>$ easy_install dpath
&gt;&gt;&gt; for (path, value) in dpath.util.search(YOUR_DICTIONARY, "morefoo/morebar", yielded=True)
</code></pre>

... and done. 'value' will hold {'bacon': 'foobar'} in that case.

blocks|key|573920|text|我所能找到的最好的库之一，另外，也是非常活跃地开发的，是一个从boto中提取的项目：JMESPath。它有一个非常强大的语法来做通常需要几页代码才能表达的事情。|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|573921|下面是一些示例：|573922|search('foo+%7C+bar',+{"foo":+{"bar":+"baz"}})+->+"baz"
search('foo[*].bar+%7C+[0]',+{
++++"foo":+[{"bar":+["first1",+"second1"]},
++++++++++++{"bar":+["first2",+"second2"]}]})+->+["first1",+"second1"]
search('foo+%7C+[0]',+{"foo":+[0,+1,+2]})+->+[0]|code-block|syntax|javascript|573923|entityMap|0|LINK|mutability|MUTABLE|url|https://jmespath.readthedocs.org/en/latest/^0|16|8|0|0|0|0^^$0|@$1|2|3|4|5|6|7|S|8|@]|9|@$A|T|B|U|1|V]]|C|$]]|$1|D|3|E|5|6|7|W|8|@]|9|@]|C|$]]|$1|F|3|G|5|H|7|X|8|@]|9|@]|C|$I|J]]|$1|K|3|-4|5|6|7|Y|8|@]|9|@]|C|$]]]|L|$M|$5|N|O|P|C|$Q|R]]]]

One of the best libraries I've been able to identify, which, in addition, is very actively developed, is an extracted project from boto: <a href="https://jmespath.readthedocs.org/en/latest/">JMESPath</a>. It has a very powerful syntax of doing things that would normally take pages of code to express.

Here are some examples:

<pre><code>search('foo | bar', {"foo": {"bar": "baz"}}) -&gt; "baz"
search('foo[*].bar | [0]', {
 "foo": [{"bar": ["first1", "second1"]},
 {"bar": ["first2", "second2"]}]}) -&gt; ["first1", "second1"]
search('foo | [0]', {"foo": [0, 1, 2]}) -&gt; [0]
</code></pre>

blocks|key|790195|text|def+Dict(var,+*arg,+**kwarg):
++"""+Return+the+value+of+an+(imbricated)+dictionnary,+if+all+fields+exist+else+return+""+unless+"default=new_value"+specified+as+end+argument
++++++Avoid+TypeError:+argument+of+type+'NoneType'+is+not+iterable
++++++Ex:+Dict(variable_dict,+'field1',+'field2',+default+=+0)
++"""
++for+key+in+arg:
++++if+isinstance(var,+dict)+and+key+and+key+in+var:++var+=+var[key]
++++else:++return+kwarg['default']+if+kwarg+and+'default'+in+kwarg+else+""+++#+Allow+Dict(var,+tvdbid).isdigit()+for+example
++return+kwarg['default']+if+var+in+(None,+'',+'N/A',+'null')+and+kwarg+and+'default'+in+kwarg+else+""+if+var+in+(None,+'',+'N/A',+'null')+else+var

foo+=+{
++'spam':'eggs',
++'morefoo':+{
+++++++++++++++'bar':'soap',
+++++++++++++++'morebar':+{'bacon'+:+'foobar'}
++++++++++++++}
+++}
print+Dict(foo,+'morefoo',+'morebar')
print+Dict(foo,+'morefoo',+'morebar',+default=None)|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|790196|我有一个SaveDict(value，var，*arg)函数，它甚至可以附加到dict中的列表...|unstyled|790197|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$B|C]]|$1|D|3|E|5|F|7|J|8|@]|9|@]|A|$]]|$1|G|3|-4|5|F|7|K|8|@]|9|@]|A|$]]]|H|$]]

<pre><code>def Dict(var, *arg, **kwarg):
 """ Return the value of an (imbricated) dictionnary, if all fields exist else return "" unless "default=new_value" specified as end argument
 Avoid TypeError: argument of type 'NoneType' is not iterable
 Ex: Dict(variable_dict, 'field1', 'field2', default = 0)
 """
 for key in arg:
 if isinstance(var, dict) and key and key in var: var = var[key]
 else: return kwarg['default'] if kwarg and 'default' in kwarg else "" # Allow Dict(var, tvdbid).isdigit() for example
 return kwarg['default'] if var in (None, '', 'N/A', 'null') and kwarg and 'default' in kwarg else "" if var in (None, '', 'N/A', 'null') else var

foo = {
 'spam':'eggs',
 'morefoo': {
 'bar':'soap',
 'morebar': {'bacon' : 'foobar'}
 }
 }
print Dict(foo, 'morefoo', 'morebar')
print Dict(foo, 'morefoo', 'morebar', default=None)
</code></pre>

Have a SaveDict(value, var, *arg) function that can even append to lists in dict...

Is there a way to define a XPath type query for nested python dictionaries.

Something like this:

<pre><code>foo = {
 'spam':'eggs',
 'morefoo': {
 'bar':'soap',
 'morebar': {'bacon' : 'foobar'}
 }
 }

print( foo.select("/morefoo/morebar") )

&gt;&gt; {'bacon' : 'foobar'}
</code></pre>

I also needed to select nested lists ;)

This can be done easily with @jellybean's solution:

<pre><code>def xpath_get(mydict, path):
 elem = mydict
 try:
 for x in path.strip("/").split("/"):
 try:
 x = int(x)
 elem = elem[x]
 except ValueError:
 elem = elem.get(x)
 except:
 pass

 return elem

foo = {
 'spam':'eggs',
 'morefoo': [{
 'bar':'soap',
 'morebar': {
 'bacon' : {
 'bla':'balbla'
 }
 }
 },
 'bla'
 ]
 }

print xpath_get(foo, "/morefoo/0/morebar/bacon")
</code></pre>

[EDIT 2016] This question and the accepted answer are ancient. The newer answers may do the job better than the original answer. However I did not test them so I won't change the accepted answer.

Xpath like query for nested python dictionaries

有没有办法为嵌套的python字典定义一个XPath类型的查询？如下所示：foo = {  'spam':'eggs',  'morefoo': {               'bar':'soap',               'morebar': {'bacon' : 'foobar'}            ...

问针对嵌套python字典的类Xpath查询
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