using regex validators in django models
from django.db import models
from django.core.validators import RegexValidator
class YourModel(models.Model):
your_field = models.CharField(
max_length=100,
validators=[
RegexValidator(
regex=r'^[A-Za-z0-9_]+$',
message='Only letters, numbers, and underscores are allowed.',
code='invalid_your_field'
),
]
)