我想在我的DJango版本2.0.2中加入this datepicket widget，但它会引发错误
请求方法：GET 请求网址：http://127.0.0.1:8000/xuser/1/edit Django版本：2.0.2 异常类型：TypeError 异常值：'JSFiles'对象不可逆 异常位置：合并中的D：\ DevTools \ Python \ lib \ site-packages \ django \ forms \ widgets.py，第114行 Python可执行文件：D：\ DevTools \ Python \ python.exe Python版本：3.6.3
我已经在以下线程中查找过类似的错误
但这些只是关于urlpatterns的拼写错误，甚至没有透露python中可逆的实际意义。关于可逆物体的google search不会产生比上述线程更多的东西。所以，我的问题是，
追溯：
Environment:
Request Method: GET
Request URL: http://127.0.0.1:8000/xuser/1/edit
Django Version: 2.0.2
Python Version: 3.6.3
Installed Applications:
['bootstrap3',
'bootstrap_datepicker',
'core.apps.CoreConfig',
'django.contrib.admin',
'django.contrib.auth',
'django.contrib.contenttypes',
'django.contrib.sessions',
'django.contrib.messages',
'django.contrib.staticfiles']
Installed Middleware:
['django.middleware.security.SecurityMiddleware',
'django.contrib.sessions.middleware.SessionMiddleware',
'django.middleware.common.CommonMiddleware',
'django.middleware.csrf.CsrfViewMiddleware',
'django.contrib.auth.middleware.AuthenticationMiddleware',
'django.contrib.messages.middleware.MessageMiddleware',
'django.middleware.clickjacking.XFrameOptionsMiddleware']
Template error:
In template D:\Python\dj_abstractbaseuser2\core\templates\core\edit.html, error at line 8
'JSFiles' object is not reversible
1 : {# Load the tag library #}
2 : {% load bootstrap3 %}
3 :
4 : {# Load CSS and JavaScript #}
5 : {% bootstrap_css %}
6 : {% bootstrap_javascript %}
7 : {% block extrahead %}
8 : {{ form.media }}
9 : {% endblock %}
10 :
11 : {# Display django.contrib.messages as Bootstrap alerts #}
12 : {% bootstrap_messages %}
13 : <form method="post">
14 : {% csrf_token %}
15 : {% bootstrap_field form.first_name %}
16 : {% bootstrap_field form.last_name %}
17 : {% bootstrap_field form.date_of_birth %}
18 : {% buttons %}
Traceback:
File "D:\DevTools\Python\lib\site-packages\django\forms\forms.py" in __getitem__
157. field = self.fields[name]
During handling of the above exception ('media'), another exception occurred:
File "D:\DevTools\Python\lib\site-packages\django\template\base.py" in _resolve_lookup
835. current = current[bit]
File "D:\DevTools\Python\lib\site-packages\django\forms\forms.py" in __getitem__
163. ', '.join(sorted(f for f in self.fields)),
During handling of the above exception ("Key 'media' not found in 'UserEditForm'. Choices are: date_of_birth, first_name, last_name."), another exception occurred:
File "D:\DevTools\Python\lib\site-packages\django\core\handlers\exception.py" in inner
35. response = get_response(request)
File "D:\DevTools\Python\lib\site-packages\django\core\handlers\base.py" in _get_response
158. response = self.process_exception_by_middleware(e, request)
File "D:\DevTools\Python\lib\site-packages\django\core\handlers\base.py" in _get_response
156. response = response.render()
File "D:\DevTools\Python\lib\site-packages\django\template\response.py" in render
106. self.content = self.rendered_content
File "D:\DevTools\Python\lib\site-packages\django\template\response.py" in rendered_content
83. content = template.render(context, self._request)
File "D:\DevTools\Python\lib\site-packages\django\template\backends\django.py" in render
61. return self.template.render(context)
File "D:\DevTools\Python\lib\site-packages\django\template\base.py" in render
175. return self._render(context)
File "D:\DevTools\Python\lib\site-packages\django\template\base.py" in _render
167. return self.nodelist.render(context)
File "D:\DevTools\Python\lib\site-packages\django\template\base.py" in render
943. bit = node.render_annotated(context)
File "D:\DevTools\Python\lib\site-packages\django\template\base.py" in render_annotated
910. return self.render(context)
File "D:\DevTools\Python\lib\site-packages\django\template\loader_tags.py" in render
58. result = self.nodelist.render(context)
File "D:\DevTools\Python\lib\site-packages\django\template\base.py" in render
943. bit = node.render_annotated(context)
File "D:\DevTools\Python\lib\site-packages\django\template\base.py" in render_annotated
910. return self.render(context)
File "D:\DevTools\Python\lib\site-packages\django\template\base.py" in render
993. output = self.filter_expression.resolve(context)
File "D:\DevTools\Python\lib\site-packages\django\template\base.py" in resolve
676. obj = self.var.resolve(context)
File "D:\DevTools\Python\lib\site-packages\django\template\base.py" in resolve
802. value = self._resolve_lookup(context)
File "D:\DevTools\Python\lib\site-packages\django\template\base.py" in _resolve_lookup
843. current = getattr(current, bit)
File "D:\DevTools\Python\lib\site-packages\django\forms\widgets.py" in _media
148. base = sup_cls.media
File "D:\DevTools\Python\lib\site-packages\django\forms\widgets.py" in _media
148. base = sup_cls.media
File "D:\DevTools\Python\lib\site-packages\django\forms\forms.py" in media
460. media = media + field.widget.media
File "D:\DevTools\Python\lib\site-packages\django\forms\widgets.py" in _media
148. base = sup_cls.media
File "D:\DevTools\Python\lib\site-packages\django\forms\widgets.py" in _media
163. return m + Media(definition)
File "D:\DevTools\Python\lib\site-packages\django\forms\widgets.py" in __add__
135. combined._js = self.merge(self._js, other._js)
File "D:\DevTools\Python\lib\site-packages\django\forms\widgets.py" in merge
114. for path in reversed(list_2):
Exception Type: TypeError at /xuser/1/edit
Exception Value: 'JSFiles' object is not reversible
该错误是由this issue提交给小部件的Github页面引起的，并且尚未解决。所以我切换到django-bootstrap-datepicker-plus，它正在我的DJango版本2.0.2正常工作。但问题仍然是需要回答。
什么是可逆物体？为什么我们得到这个错误？
python内置函数reversed引发了错误，该函数将序列作为唯一参数并反转序列。
reversed() Parameters seq - 应该颠倒的序列。
- 可以是支持序列协议（
__len__()和__getitem__()方法）作为元组，字符串，列表或范围的对象- 可能是已实现
__reversed__()的对象
因此所有序列（例如，列表，元组）都是可逆的。但是为了使对象可逆，我们需要实现一个名为__reversed__的方法，或者__len__()和__getitem__()方法。如果我们将一个对象传递给不符合上述任何条件的reversed()函数，它将引发异常TypeError - object is not reversible。
DJango 2.0将此reversed()功能用于任何小部件添加的资产。由于上述窗口小部件中使用的JSFiles对象未实现可逆条件，因此会引发错误。