request.POST.get('username') returns NONE - django

Question

def profile(request):
Exist_Emails = User.objects.filter(is_active=True).values_list('email', flat=True)
Exist_Usernames = User.objects.filter(is_active=True).values_list('username', flat=True)
current_user = User.objects.get(username=request.user.username)
Email_Invalid = False
Username_Invalid = False
if request.method != 'POST':
u_form = UserUpdateForm(instance=request.user)
p_form = ProfileUpdateForm(instance=request.user.profile)
else:
update_username = request.POST.get('username')
u_form = UserUpdateForm(request.POST, instance=request.user)
p_form = ProfileUpdateForm(request.POST,
request.FILES,
instance=request.user.profile)
if u_form.is_valid() and p_form.is_valid():
p_form.save()
update_u_form = u_form.save(commit=False)
#Problem occurs in this if statement!
if update_u_form.username in Exist_Usernames and update_u_form.username != current_user.username:
Username_Invalid = True
u_form = UserUpdateForm(instance=current_user) ##
messages.error(request, 'The username already eixts')
#But it worked in this elif statement which is almost the same!
elif update_u_form.email in Exist_Emails and update_u_form.email != current_user.email:
Email_Invalid = True
u_form = UserUpdateForm(instance=current_user)
messages.error(request, 'The email already exits.')
else:
update_u_form.save()
return redirect('/users/profile/')
context = {
'u_form': u_form, 'p_form': p_form,'update_username':
update_username,'Email_Invalid': Email_Invalid,'current_user':
current_user, 'Username_Invalid': Username_Invalid}
return render(request, 'users/profile.html', context)
This is the html template:
{% if Email_Invalid == "True" or Username_Invalid == "True" %}
{{ current_user.username }}
</div>
<div style="font-size:16px;">
{{ current_user.email }}
</div>
<p>"Sorry, the email or username already exits."</p>
{% else %}
{{ user.username }}
</div>
<div style="font-size:16px;">
{{ user.email }}
</div>
{% endif %}
{{Username_Invalid}}
{{update_username}}
<form method="post" class="form" enctype="multipart/form-data">
{% csrf_token %}
{{ u_form.as_p }}
{{ p_form.as_p }}
<button name="sumbit" class="btn btn-primary" >Update</button>
</form>
My forms.py:
class UserUpdateForm(forms.ModelForm):
email = forms.EmailField()
class Meta:
model = User
fields = ['username', 'email']
As I type in updated username, and press submit. However The {{Username_Invalid}} returns False which is supposed to be True in if statement.
Then I checked {{update_username}} which returns NONE!! update_username here is just request.POST.get('username').
What is going on? I thought UserUpdateForm should inherit from User model. So request.POST should have a dictionary key-value pair 'username':username.
My debugging process:
What I am trying to do is to display (instance = current_user) in u_form when the user tries to edit email or username but these email or username has already been registered in database by others.
It works perfectly fine in the email field, but when I edit username to be sth that has already been registered by another user, the instance however displays whatever I typed in(It should print instance = current_user not request.user).
So I found out that when I did this , it didn't enter the first IF statement after is_valid, as Username_Invalid still prints False. Then I checked if something is wrong with 'update_u_form.username' , so I set
update_username = request.POST.get('username')
to print out the value, and it returns NONE. I think this is where the problem is but can't figure out why.