[尝试在Django应用上搜索书籍时，出现KeyError。数据库中没有书籍记录。但是'isbn_list_of_dicts'被分配给request.sessions。似乎是什么问题？如果没有记录，为什么不显示状态消息？
def search(request):
"""Book search based on authors, and/or publisher, and/or title, and/or subject"""
if request.method == 'GET':
# create a form instance and populate it with data from the request:
form = SearchForm(request.GET)
# print (request.GET['search_value'])
isbn_list_of_dicts = []
# check whether it's valid:
if form.is_valid():
temp_dict = {}
# Gets the search values, which is determined by what the user has typed into search bar
search_values = form.cleaned_data['search_value'].split(" ")
search_values = list(filter(None, search_values))
#print ("Search form")
#print (search_values)
# calls the query function to get list of dictionaries of book data
isbn_list_of_dicts = query(search_values, 'all')
# No such results could be found
if len(isbn_list_of_dicts) == 0:
return render(request, 'bookstore/search_results.html', {'books': request.session['isbn_list_of_dicts'], 'status': 'No results could be found :('})
request.session['isbn_list_of_dicts'] = isbn_list_of_dicts
request.session.modified = True
return render(request, 'bookstore/search_results.html', {'books': request.session['isbn_list_of_dicts'] , 'status': 'Search results for "%s"'%(' '.join(search_values))})
# Filters the search results by author
def search_filter_author(request):
return render(request, 'bookstore/search_filter_author.html', {'books': request.session['isbn_list_of_dicts']})
# Filters the search results by year
def search_filter_year(request):
return render(request, 'bookstore/search_filter_year.html', {'books': request.session['isbn_list_of_dicts']})
堆栈跟踪：
Environment:
Request Method: GET
Request URL: http://127.0.0.1:8000/bookstore/search/?search_value=Dan+Brown
Django Version: 3.0.2
Python Version: 3.7.4
Installed Applications:
['polls.apps.PollsConfig',
'bookstore.apps.BookstoreConfig',
'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']
Traceback (most recent call last):
File "C:\Python37\lib\site-packages\django\core\handlers\exception.py", line 34, in inner
response = get_response(request)
File "C:\Python37\lib\site-packages\django\core\handlers\base.py", line 115, in _get_response
response = self.process_exception_by_middleware(e, request)
File "C:\Python37\lib\site-packages\django\core\handlers\base.py", line 113, in _get_response
response = wrapped_callback(request, *callback_args, **callback_kwargs)
File "C:\Users\Kaleab\Desktop\bookstore\django-bookstore\db-project\bookstore\views.py", line 70, in search
return render(request, 'bookstore/search_results.html', {'books': request.session['isbn_list_of_dicts'], 'status': 'No results could be found :('})
File "C:\Python37\lib\site-packages\django\contrib\sessions\backends\base.py", line 64, in __getitem__
return self._session[key]
Exception Type: KeyError at /bookstore/search/
Exception Value: 'isbn_list_of_dicts'
我在这里可以理解的是，如果isbn_list_of_dicts的长度为0，您就不会在会话中存储数据。因此，最好在此之前存储它，或者像这样传递变量：
isbn_list_of_dicts = query(search_values, 'all')
# No such results could be found
if len(isbn_list_of_dicts) == 0:
return render(request, 'bookstore/search_results.html', {'books': isbn_list_of_dicts, 'status': 'No results could be found :('})