how to create validator for lowercase user in Django 2.0?

Question

my site is up and running. However, silly me I didnt put in a validator to check if users and username can only be in lower-case (I only realised that DJANGO allowed capitalized Users and usernames). Although, I have put up a warning but users usually ignore that still write upper case letters or alteast capitalized letters in their signup forms. I then encounter the problem of slugs not working, thereafter I have to manually change their usernames. I do not want to change the behavior of slugs and instead can I please ask for help from someone in changing my views? I have tried .lower() .format() as well and it didnt work. I am very weak on validators.

forms.py

from django.contrib.auth.models import User
from django import forms
from captcha.fields import CaptchaField

class SignUpForm(forms.ModelForm):

    captcha = CaptchaField()
    password = forms.CharField(max_length= 15, widget=forms.PasswordInput)

    class Meta:
           model = User
           fields = ['username', 'email', 'password']

Views.py

   from django.shortcuts import render, redirect
   from django.http import HttpResponse
   from django.contrib.auth import authenticate, login
   from django.views import generic
   from django.views.generic import View
   from home.forms import SignUpForm



  class SignUpFormView(View):
form_class = SignUpForm
template_name = 'home/signup.html'

#if there is no sign up yet
def get(self,request):
    form = self.form_class(None)
    return render(request, self.template_name, {'form': form})


#if going to sig up
def post(self,request):
    form = self.form_class(request.POST)


    if form.is_valid():
        #it takes information but does save it
        user = form.save(commit = False)
        #cleaned normalized data
        username = form.cleaned_data['username']
        password = form.cleaned_data['password']
        user.set_password(password)
        user.save()




        #returns if it is all correct

        user = authenticate(username = username, password = password)

        if user is not None:

            if user.is_active:
                login(request, user)
                return redirect("userprofile:newprofile")

    return render(request, self.template_name, {'form': form})

Asked By: Fahad Sher

||

Source

Answer 1

You can add a validation in the SignupForm:

from django.contrib.auth.models import User
from django import forms
from captcha.fields import CaptchaField

class SignUpForm(forms.ModelForm):

    captcha = CaptchaField()
    password = forms.CharField(max_length= 15, widget=forms.PasswordInput)

    def clean_username(self):
        data = self.cleaned_data['username']
        if not data.islower():
            raise forms.ValidationError("Usernames should be in lowercase")
        return data

    class Meta:
           model = User
           fields = ['username', 'email', 'password']

So in case the data.islower() check fails (the username contains uppercase characters), it will raise a ValidationError, and thus the form is not valid.

Note that islower() only checks case-based characters, so if the string contains digits, it will still succeed. You thus might want to finetune the check. Or as specified in the documentation of str.islower:

Return True if all cased characters in the string are lowercase and
there is at least one cased character, False otherwise.

An alternative might be to convert the data to lowercase, such that a user that enters 'FooBar' gets as username foobar, although this can result in the fact that users get confused that the username they picked is not the username they get.

Answered By: Willem Van Onsem

Answer 2

Change username = form.cleaned_data['username'] to username = form.cleaned_data['username'].lower()

Answered By: a_k_v

Answer 3

You can create a validator.

create validators.py

from django.core.exceptions import ValidationError


def validate_lower_case(value):
    if not value.islower():
        raise ValidationError('You must use only lowercase letters!')

your models

from django.db import models
from .validators import validate_lower_case


class User(models.Model):
    first_name = models.CharField(validators=[validate_lower_case])

Answered By: Mehrdad Mahmoodpoor

how to create validator for lowercase user in Django 2.0?

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