How to continue in loop until correct input received

[sunnyarora]

Sir, by which code loop is getting terminated if right input received?

---

Error:
Sir if I applied below code in my program then function is showing unresolved name (not linking with function)

        while True:
            fname=input("Enter Father's First name")
            fname = fname.lower()
            if(fname.isalpha()):
                addfname(fname)
                while True:
                    pass

Whereas below code is working fine

        while True:
            name=input("Enter Customer First Name")
            name=name.lower()
            if(name.isalpha()):
                addname(name)
                while True:
                    pass