在字典中的python中,如果key
是byte string
,那么json.dumps
将抛出错误,因此我尝试在将所有keys
传递给json.dumps
之前,将它们递归地转换为string
Note: json.dumps converts the value to str using default function but not keys
以下是我的函数,它将检查任何byte string keys
并将它们转换为string
:
def keys_string(d):
rval = {}
if not isinstance(d, dict):
if isinstance(d,(tuple,list,set)):
v = [keys_string(x) for x in d]
return v
else:
return d
for k,v in d.items():
if isinstance(k,bytes):
k = k.decode()
if isinstance(v,dict):
v = keys_string(v)
elif isinstance(v,(tuple,list,set)):
v = [keys_string(x) for x in v]
rval[k] = v
return rval
我正在用django调试一些代码
我想在代码的某一点检查request
对象
所以我有
request_dir = dir(request)
然后使用keys_string
将任何字节键转换为字符串(否则json转储将抛出错误)
request_dir_keys_stringed = keys_string(request_dir)
最后
json.dumps(request_dir_keys_stringed, indent=4, sort_keys=True, default=str)
当我试图做request_dir_keys_stringed = keys_string(request_dir)
时,它说
in keys_string
for k,v in d.items():
RuntimeError: dictionary changed size during iteration
我发现这种情况发生在:
k: user
和v: <SimpleLazyObject: <User: test@gmail.com>>
我尝试了request.session
对象,但它不会抛出这样的错误。但有些物体确实如此
request_session_dir = dir(request.session)
request_session_dir_keys_stringed = keys_string(request_session_dir)
json.dumps(request_session_dir_keys_stringed, indent=4, sort_keys=True, default=str)
在这种情况下该怎么办
复制问题的更多信息:
$ python --version
Python 3.7.3
$ django-admin --version
2.2.6
def articles(request):
request_dir = dir(request)
request_dir_keys_stringed = keys_string(request_dir)
print(json.dumps(request_dir_keys_stringed, indent=4, sort_keys=True, default=str)
return render(request, 'articles/main_page/articles.html')
实施解决方案后,密钥字符串变为:
def keys_string(d):
rval = {}
if not isinstance(d, dict):
if isinstance(d,(tuple,list,set)):
v = [keys_string(x) for x in d]
return v
else:
return d
keys = list(d.keys())
for k in keys:
v = d[k]
if isinstance(k,bytes):
k = k.decode()
if isinstance(v,dict):
v = keys_string(v)
elif isinstance(v,(tuple,list,set)):
v = [keys_string(x) for x in v]
rval[k] = v
return rval
request_dir = dir(request)
request_dir_keys_stringed = keys_string(request_dir)
print(json.dumps(request_dir_keys_stringed, indent=4, sort_keys=True, default=str)
现在显示的请求对象没有任何错误
request.user
是SimpleLazyObject
,它持有一个回调,该回调是一个闭包,它持有对同一request
对象的引用。然后,该回调通过创建新的attrrequest._cached_user
来更新request
对象(如果它不存在)。因此,观察request.user
可能会创建一个新的request._cached_user
属性A我认为用代码摘录来解释它更容易
来自django源代码:
因此,如果您想拥有更稳定的遍历字典键,则需要迭代dict的键副本:
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