Django No local variable error - django

Question

I have a problem with one of my functions . I receive this error when I submit a post form without any value.
local variable 'picture' referenced before assignment
Traceback:
File "C:\Python26\Lib\site-packages\django\core\handlers\base.py" in get_response
111. response = callback(request, *callback_args, **callback_kwargs)
File "C:\o\17\mysite\pet\views.py" in BoardEditor
260. return render(request,'boardeditor.html', {'picture':picture,'board':BoardNameForm(request.user),'boardpicture':BoardPictureForm(request.user),})
I think I understand what causing the problem because in my views. I have a picture variable that retrieves all my pictures and if their no value coming from POST . I get this error .
I'm been searching and trying for solutions on how to handle if variable is None and I haven't been successful.
Here are the solutions I tried from all the resources i gathered
If board is None , assign it an empty value.
if forms.is_valid():
board = forms.cleaned_data['board']
if board == None:
picture = ""
How can I combat the error when their is no value toward my picture variable?

Answer 1

You will get this error when your form doesn't validate ( is_valid() return false), so in this case you don't have picture defined at all.
You can just create a context dictionary at begin and then put there variables you want. Something like this
context_data = {}
if form.is_valid():
context_data['picture']=Picture.objects.filter(board=boards)
return render(request,'boardeditor.html',context_data)

Answer 2

[..........]
if forms.is_valid():
board = forms.cleaned_data['board']
picture = "" //<--add
if board:
boards = forms.cleaned_data['board']
picture = Picture.objects.filter(board=boards)
return render(request,'boardeditor.html',{ // align with if board:
'picture':picture,
'board':BoardNameForm(request.user),
'boardpicture':BoardPictureForm(request.user),
})
if formss.is_valid():
pooh = forms.cleaned_data['board']
pict = "" //<--add
if pooh:
pooh = formss.cleaned_data['board']
pict = Picture.objects.filter(board=pooh)
return render(request,'boardeditor.html',{ // align with if pooh:
'pict':pict,
'board':BoardNameForm(request.user),
'boardpicture':BoardPictureForm(request.user),
})
[..........]

Answer 3

Following is the line that causes the error:
return render(request,'boardeditor.html',{'picture':picture,'board':BoardNameForm(request.user),'boardpicture':BoardPictureForm(request.user),})
Reason being that the return statement is not under the if condition so it tries returning the picture variable under all circumstances. So according to your code:
if forms.is_valid():
board = forms.cleaned_data['board']
if board == None:
picture = ""
if board:
boards = forms.cleaned_data['board']
picture = Picture.objects.filter(board=boards)
return render(request,'boardeditor.html',{'picture':picture,'board':BoardNameForm(request.user),'boardpicture':BoardPictureForm(request.user),})
if the if forms.is_valid() condition fails, you are still trying to return picture variable which is undefined. You need to make sure you define the variable before accessing it.
There are a plenty of ways you can do this. For Example:
Example 1:
if forms.is_valid():
board = forms.cleaned_data['board']
if board:
boards = forms.cleaned_data['board']
picture = Picture.objects.filter(board=boards)
else:
picture = '' # or None or False or Whatever
return render(request,'boardeditor.html',{'picture':picture,'board':BoardNameForm(request.user),'boardpicture':BoardPictureForm(request.user),})
Example 2:
picture = '' # or None or False or Whatever
if forms.is_valid():
board = forms.cleaned_data['board']
if board:
boards = forms.cleaned_data['board']
picture = Picture.objects.filter(board=boards)
return render(request,'boardeditor.html',{'picture':picture,'board':BoardNameForm(request.user),'boardpicture':BoardPictureForm(request.user),})
Example 3:
if forms.is_valid():
board = forms.cleaned_data['board']
if board:
boards = forms.cleaned_data['board']
picture = Picture.objects.filter(board=boards)
return render(request,'boardeditor.html',{'picture':picture,'board':BoardNameForm(request.user),'boardpicture':BoardPictureForm(request.user),})
else:
return render(request,'boardeditor.html',{'picture':'','board':BoardNameForm(request.user),'boardpicture':BoardPictureForm(request.user),})
or put all the variables in a dictionary as Aldarund suggested and them pass the dictionary to the context.