Not really a Django question, just basic Python.
For starters strip() will remove only leading and trailing chars in the set, not embedded chars.
Curiously though, with all due respect, this:
if dataless.isdigit() != True:
has beginner written all over it. What's wrong with:
if not dataless.isdigit():
Comparing booleans by value is an interesting notion.
But personally, Django is rooted on the principle of DRY (Don't Repeat Yourself) and if I wanted to store phone numbers I'd look to see who's done it already and lo and behold
django-phonenumber-field!
https://github.com/stefanfoulis/django-phonenumber-fieldTry that maybe and save yourself a lot of thinking and hassle on the phone number formats.
Regards,
Bernd.