class UserCreationForm(forms.ModelForm):
    """
    A form that creates a user, with no privileges, from the given username and password.
    """
    username = forms.RegexField(label=_("Username"), max_length=30, regex=r'^\w+$',
        help_text = _("Required. 30 characters or fewer. Alphanumeric characters only (letters, digits and underscores)."),
        error_message = _("This value must contain only letters, numbers and underscores."))
    password1 = forms.CharField(label=_("Password"), widget=forms.PasswordInput)
    password2 = forms.CharField(label=_("Password confirmation"), widget=forms.PasswordInput,
        help_text = _("Enter the same password as above, for verification."))

....................

<p>
    {{ form.username.errors }}
    <label for="id_username">{% trans "Имя пользователя" %}<span class="blue">*</span> :</label><br />
    {{ form.username }}
    <span>{{ form.username.help_text }}</span>
</p>

form = UserCreationForm()
print(form.username)