35.Validate Numeric Strings in Python (Interview Trick)

Описание: Learn how to check if a string contains only digits in Python using three methods: str.isdigit(), a manual loop, and Regex. We’ll accept user input, show example runs, and explain edge cases (like empty strings). Perfect for coding interviews, validation logic, and beginner Python practice.

Code covered: isdigit(), ASCII range checks, re.fullmatch(r"\d+").
Use cases: validating PIN/OTP, numeric fields, data cleaning.

#Python #StringValidation #Regex #CodingInterview #BeginnerPython #PythonTips