blocks|key|1351807|text|除了基本类型之外，json不能用于序列化任何类型，如dict、list、int/long和string(这并不全面)。例如，即使这些简单的命令也不起作用：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1351808|import+json
json.dumps(object())|code-block|syntax|javascript|1351809|如果您想序列化django对象，您应该参考django+documentation+on+serialization，它将使用自己的库，但它们确实支持json。|offset|length|1351810|entityMap|0|LINK|mutability|MUTABLE|url|http://docs.djangoproject.com/en/dev/topics/serialization/^0|0|0|L|11|0|0^^$0|@$1|2|3|4|5|6|7|S|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|T|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|U|8|@]|9|@$I|V|J|W|1|X]]|A|$]]|$1|K|3|-4|5|6|7|Y|8|@]|9|@]|A|$]]]|L|$M|$5|N|O|P|A|$Q|R]]]]

json cannot be used to serialize anything more than basic types such as dicts, lists, ints/longs, and strings (this is not comprehensive). For example, even these simple commands do not work:

<pre><code>import json
json.dumps(object())
</code></pre>

If you want to serialize django objects, you should refer to the <a href="http://docs.djangoproject.com/en/dev/topics/serialization/" rel="nofollow noreferrer">django documentation on serialization</a>, which will use their own libraries, but they do do support json.

blocks|key|1136448|text|由于找不到合适的解决方案，我编写了自己的解决方案，它不完全是JSON序列化程序，而是Javascript序列化程序|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1136449|from+google.appengine.ext+import+db
from+google.appengine.api.datastore_types+import+*

def+dumpStr(obj):
++++return+"'"+%2B+obj+%2B+"'"

def+dumps(obj):
++++if+isinstance(obj,+str):
++++++++return+dumpStr(obj)
++++elif+obj+==+None:
++++++++return+None
++++elif+isinstance(obj,+list):
++++++++items+=+[];
++++++++for+item+in+obj:
++++++++++++items.append(dumps(item))
++++++++return+'['+%2B+','.join(items)+%2B+']'
++++elif+isinstance(obj,+datetime.datetime):
++++++++return+"new+Date('%25s')"+%25+obj.ctime()
++++properties+=+[];
++++for+property+in+dir(obj):
++++++++if+property[0]+!=+'_':
++++++++++++value+=+obj.__getattribute__(property)
++++++++++++valueClass+=+str(value.__class__)
++++++++++++if+not(('function'+in+valueClass)+or+('built'+in+valueClass)+or+('method'+in+valueClass)):
++++++++++++++++value+=+dumps(value)
++++++++++++++++if+value+!=+None:
++++++++++++++++++++properties.append("'"+%2B+property+%2B+"':"+%2B+value)
++++if+len(properties)+==+0:
++++++++return+str(obj)
++++else:
++++++++return+'{'+%2B+','.join(properties)+%2B+'}'|code-block|syntax|javascript|1136450|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|$]]

Since I could not find an appropriate solution I wrote my own, which is not exactly a JSON serializer, but a Javascript serializer

<pre><code>from google.appengine.ext import db
from google.appengine.api.datastore_types import *

def dumpStr(obj):
 return "'" + obj + "'"

def dumps(obj):
 if isinstance(obj, str):
 return dumpStr(obj)
 elif obj == None:
 return None
 elif isinstance(obj, list):
 items = [];
 for item in obj:
 items.append(dumps(item))
 return '[' + ','.join(items) + ']'
 elif isinstance(obj, datetime.datetime):
 return "new Date('%s')" % obj.ctime()
 properties = [];
 for property in dir(obj):
 if property[0] != '_':
 value = obj.__getattribute__(property)
 valueClass = str(value.__class__)
 if not(('function' in valueClass) or ('built' in valueClass) or ('method' in valueClass)):
 value = dumps(value)
 if value != None:
 properties.append("'" + property + "':" + value)
 if len(properties) == 0:
 return str(obj)
 else:
 return '{' + ','.join(properties) + '}'
</code></pre>

blocks|key|1351909|text|据我所知--我是python的新手--使用google+app+engine的工作就是将模型对象序列化为dictioanry+python对象，然后使用简单的json将其转储为json字符串--这对我来说毫无意义--也许有人知道如何序列化到ditionary+(pickel?)这方面的任何帮助都是有帮助的！谷歌应用程序引擎没有内置的解决方案，这一点并不令人印象深刻。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1351910|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|$]]

From what i can understand - and i am new to python - with google app engine the work around is to serialize the model object to a dictioanry python object and then use simple json to dump it as a json string - this makes no sense to me - maybe someone has the know to serialise to a ditionary (pickel?)
Any help on this would be HELP! not to impressed that google app engine has no inbuilt solution for this.

blocks|key|1136553|text|Jader+Dias提供的示例在经过一些调整后可以很好地满足我的关注。移除encode方法，因为它包含循环引用。调整后的类应该如下所示：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1136554|import+datetime++
import+time+

from+google.appengine.api+import+users+
from+google.appengine.ext+import+db+
from+django.utils+import+simplejson++


class+GqlEncoder(simplejson.JSONEncoder):+

++++"""Extends+JSONEncoder+to+add+support+for+GQL+results+and+properties.+

++++Adds+support+to+simplejson+JSONEncoders+for+GQL+results+and+properties+by+
++++overriding+JSONEncoder's+default+method.+
++++"""+

++++#+TODO+Improve+coverage+for+all+of+App+Engine's+Property+types.+

++++def+default(self,+obj):+

++++++++"""Tests+the+input+object,+obj,+to+encode+as+JSON."""+

++++++++if+hasattr(obj,+'__json__'):+
++++++++++++return+getattr(obj,+'__json__')()+

++++++++if+isinstance(obj,+db.GqlQuery):+
++++++++++++return+list(obj)+
++++++++
++++++++elif+isinstance(obj,+db.Model):+
++++++++++++properties+=+obj.properties().items()+
++++++++++++output+=+{}+
++++++++++++for+field,+value+in+properties:+
++++++++++++++++output[field]+=+getattr(obj,+field)+
++++++++++++return+output+
++++++++
++++++++elif+isinstance(obj,+datetime.datetime):+
++++++++++++output+=+{}+
++++++++++++fields+=+['day',+'hour',+'microsecond',+'minute',+'month',+'second',+'year']+
++++++++++++methods+=+['ctime',+'isocalendar',+'isoformat',+'isoweekday',+'timetuple']+
++++++++++++for+field+in+fields:+
++++++++++++++++output[field]+=+getattr(obj,+field)+
++++++++++++for+method+in+methods:+
++++++++++++++++output[method]+=+getattr(obj,+method)()+
++++++++++++output['epoch']+=+time.mktime(obj.timetuple())+
++++++++++++return+output

++++++++elif+isinstance(obj,+datetime.date):+
++++++++++++output+=+{}+
++++++++++++fields+=+['year',+'month',+'day']+
++++++++++++methods+=+['ctime',+'isocalendar',+'isoformat',+'isoweekday',+'timetuple']+
++++++++++++for+field+in+fields:+
++++++++++++++++output[field]+=+getattr(obj,+field)+
++++++++++++for+method+in+methods:+
++++++++++++++++output[method]+=+getattr(obj,+method)()+
++++++++++++output['epoch']+=+time.mktime(obj.timetuple())+
++++++++++++return+output+
++++++++
++++++++elif+isinstance(obj,+time.struct_time):+
++++++++++++return+list(obj)+
++++++++
++++++++elif+isinstance(obj,+users.User):+
++++++++++++output+=+{}+
++++++++++++methods+=+['nickname',+'email',+'auth_domain']+
++++++++++++for+method+in+methods:+
++++++++++++++++output[method]+=+getattr(obj,+method)()+
++++++++++++return+output+
++++++++
++++++++return+simplejson.JSONEncoder.default(self,+obj)+|code-block|syntax|javascript|1136555|因为我已经将这个类保存在一个名为utils.py的文件中，并在适当的时候使用|offset|length|style|CODE|1136556|import+utils|1136557|然后我调用utils.GqlEncoder().encode(results)，例如：|1136558|query+=+User.all()
results+=+query.fetch(10)
++++++++++++
self.response.headers['Content-Type']+=+"text/plain"+#+Alt.+application/json
self.response.out.write(+utils.GqlEncoder().encode(results)+)|1136559|结果应该如下所示(我添加了一些换行符，以使其更容易阅读)：|1136560|[
{"date":+{"ctime":+"Tue+Feb+23+10:41:21+2010",+"hour":+10,+"isoweekday":+2,+"month":+2,+
++++++++"second":+21,+"microsecond":+495535,+"isocalendar":+[2010,+8,+2],+"timetuple":+[2010,+2,+23,+10,+41,+21,+1,+54,+-1],+
++++++++"year":+2010,+"epoch":+1266921681.0,+"isoformat":+"2010-02-23T10:41:21.495535",+"day":+23,+"minute":+41},+
"claimed_id":+"https:\/\/www.google.com\/accounts\/o8\/id?id=abcdefghijklmnopqrstuvxyz",+
"display_name":+"Alfred+E+Neumann",+
"email":+null,+
"full_name":+"Alfred+E+Neumann"
},+
{"date":+{"ctime":+"Tue+Feb+23+11:00:54+2010",+"hour":+11,+"isoweekday":+2,+"month":+2,+
++++++++"second":+54,+"microsecond":+805261,+"isocalendar":+[2010,+8,+2],+"timetuple":+[2010,+2,+23,+11,+0,+54,+1,+54,+-1],+
++++++++"year":+2010,+"epoch":+1266922854.0,+"isoformat":+"2010-02-23T11:00:54.805261",+"day":+23,+"minute":+0},+
"claimed_id":+"http:\/\/openid.domain.net\/john",+
"display_name":+"",+
"email":+"jd@domain.net",+
"full_name":+"John+Doe"
}
]|1136561|entityMap^0|0|0|G|8|0|0|5|Y|0|0|0|0^^$0|@$1|2|3|4|5|6|7|Y|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|Z|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|10|8|@$I|11|J|12|K|L]]|9|@]|A|$]]|$1|M|3|N|5|D|7|13|8|@]|9|@]|A|$E|F]]|$1|O|3|P|5|6|7|14|8|@$I|15|J|16|K|L]]|9|@]|A|$]]|$1|Q|3|R|5|D|7|17|8|@]|9|@]|A|$E|F]]|$1|S|3|T|5|6|7|18|8|@]|9|@]|A|$]]|$1|U|3|V|5|D|7|19|8|@]|9|@]|A|$E|F]]|$1|W|3|-4|5|6|7|1A|8|@]|9|@]|A|$]]]|X|$]]

The example provided by Jader Dias works fine for my concern after some tweaking. Remove the encode method as it contains a circular reference. The adjusted class should look like:
<pre><code>import datetime 
import time 

from google.appengine.api import users 
from google.appengine.ext import db 
from django.utils import simplejson 


class GqlEncoder(simplejson.JSONEncoder): 

 &quot;&quot;&quot;Extends JSONEncoder to add support for GQL results and properties. 

 Adds support to simplejson JSONEncoders for GQL results and properties by 
 overriding JSONEncoder's default method. 
 &quot;&quot;&quot; 

 # TODO Improve coverage for all of App Engine's Property types. 

 def default(self, obj): 

 &quot;&quot;&quot;Tests the input object, obj, to encode as JSON.&quot;&quot;&quot; 

 if hasattr(obj, '__json__'): 
 return getattr(obj, '__json__')() 

 if isinstance(obj, db.GqlQuery): 
 return list(obj) 
 
 elif isinstance(obj, db.Model): 
 properties = obj.properties().items() 
 output = {} 
 for field, value in properties: 
 output[field] = getattr(obj, field) 
 return output 
 
 elif isinstance(obj, datetime.datetime): 
 output = {} 
 fields = ['day', 'hour', 'microsecond', 'minute', 'month', 'second', 'year'] 
 methods = ['ctime', 'isocalendar', 'isoformat', 'isoweekday', 'timetuple'] 
 for field in fields: 
 output[field] = getattr(obj, field) 
 for method in methods: 
 output[method] = getattr(obj, method)() 
 output['epoch'] = time.mktime(obj.timetuple()) 
 return output

 elif isinstance(obj, datetime.date): 
 output = {} 
 fields = ['year', 'month', 'day'] 
 methods = ['ctime', 'isocalendar', 'isoformat', 'isoweekday', 'timetuple'] 
 for field in fields: 
 output[field] = getattr(obj, field) 
 for method in methods: 
 output[method] = getattr(obj, method)() 
 output['epoch'] = time.mktime(obj.timetuple()) 
 return output 
 
 elif isinstance(obj, time.struct_time): 
 return list(obj) 
 
 elif isinstance(obj, users.User): 
 output = {} 
 methods = ['nickname', 'email', 'auth_domain'] 
 for method in methods: 
 output[method] = getattr(obj, method)() 
 return output 
 
 return simplejson.JSONEncoder.default(self, obj) 
</code></pre>
As I've saved this class in a file called <code>utils.py</code> and when appropriate I import it using
<pre><code>import utils
</code></pre>
Then I just call <code>utils.GqlEncoder().encode(results)</code>, for example:
<pre><code>query = User.all()
results = query.fetch(10)
 
self.response.headers['Content-Type'] = &quot;text/plain&quot; # Alt. application/json
self.response.out.write( utils.GqlEncoder().encode(results) )
</code></pre>
The result should look something like this (I've added some line feeds in order to make it a bit easier to read):
<pre><code>[
{&quot;date&quot;: {&quot;ctime&quot;: &quot;Tue Feb 23 10:41:21 2010&quot;, &quot;hour&quot;: 10, &quot;isoweekday&quot;: 2, &quot;month&quot;: 2, 
 &quot;second&quot;: 21, &quot;microsecond&quot;: 495535, &quot;isocalendar&quot;: [2010, 8, 2], &quot;timetuple&quot;: [2010, 2, 23, 10, 41, 21, 1, 54, -1], 
 &quot;year&quot;: 2010, &quot;epoch&quot;: 1266921681.0, &quot;isoformat&quot;: &quot;2010-02-23T10:41:21.495535&quot;, &quot;day&quot;: 23, &quot;minute&quot;: 41}, 
&quot;claimed_id&quot;: &quot;https:\/\/www.google.com\/accounts\/o8\/id?id=abcdefghijklmnopqrstuvxyz&quot;, 
&quot;display_name&quot;: &quot;Alfred E Neumann&quot;, 
&quot;email&quot;: null, 
&quot;full_name&quot;: &quot;Alfred E Neumann&quot;
}, 
{&quot;date&quot;: {&quot;ctime&quot;: &quot;Tue Feb 23 11:00:54 2010&quot;, &quot;hour&quot;: 11, &quot;isoweekday&quot;: 2, &quot;month&quot;: 2, 
 &quot;second&quot;: 54, &quot;microsecond&quot;: 805261, &quot;isocalendar&quot;: [2010, 8, 2], &quot;timetuple&quot;: [2010, 2, 23, 11, 0, 54, 1, 54, -1], 
 &quot;year&quot;: 2010, &quot;epoch&quot;: 1266922854.0, &quot;isoformat&quot;: &quot;2010-02-23T11:00:54.805261&quot;, &quot;day&quot;: 23, &quot;minute&quot;: 0}, 
&quot;claimed_id&quot;: &quot;http:\/\/openid.domain.net\/john&quot;, 
&quot;display_name&quot;: &quot;&quot;, 
&quot;email&quot;: &quot;jd@domain.net&quot;, 
&quot;full_name&quot;: &quot;John Doe&quot;
}
]
</code></pre>

When using

<pre><code>from django.utils import simplejson
</code></pre>

on objects of types that derive from <code>db.Model</code> it throws exceptions. How to circumvent this?

How to serialize db.Model objects to json?

在使用时from django.utils import simplejson对于从db.Model派生的类型的对象，它会抛出异常。如何规避这一点？

问如何将db.Model对象序列化为json？
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