isdigit() — Python Technical Interview Questions & Answers

isdigit()

isdigit()

  • isdigit is a string helper. You call it on text like "Asha" or "banana". It gives a new string (or a number/True-False). The old string does not change unless you assign the result back.
  • isdigit() — output: True then False.
  • Fresher trap: writing s.isdigit() and expecting s to update. Strings are immutable. Write s = s.isdigit(...) if you need the new value (when it returns a string).

Technical Interview Tip: Call isdigit on one real word and say what prints.

Code Examples for isdigit()

Example

# isdigit()
print("21".isdigit())
print("21a".isdigit())

isdigit() — output: True then False.

How to Explain isdigit() to an Interviewer

Explain isdigit() as if you are teaching a junior — definition, then one tiny script.

isdigit works on str. isdigit usually returns a new string.

What does the example print, and why?

isdigit() — output: True then False

What mistake do freshers make with isdigit()?

isdigit does not change the original string in place.