models.py:

from django.core import validators
from django.contrib.auth import get_user_model

User = get_user_model()

class ModelName(models.Model):
    LANG_HTML = 'html'
    LANG_CSS = 'css'

    LANG_CHOICES = (
        (LANG_HTML, 'HTML'),
        (LANG_CSS, 'CSS')
    )
    user = models.ForeignKey(User, on_delete=models.CASCADE)
    lang = models.CharField(
        max_length=100,
        choices=LANG_CHOICES
    )
    value = models.PositiveSmallIntegerField(max_length=3,validators=(validators.MaxLengthValidator(100)))