isalnum() — Python Technical Interview Questions & Answers

isalnum()

isalnum()

  • isalnum 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.
  • isalnum() — output: True then False. Space is not alnum.
  • Fresher trap: writing s.isalnum() and expecting s to update. Strings are immutable. Write s = s.isalnum(...) if you need the new value (when it returns a string).

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

Code Examples for isalnum()

Example

# isalnum()
print("Asha12".isalnum())
print("Asha 12".isalnum())

isalnum() — output: True then False. Space is not alnum.

How to Explain isalnum() to an Interviewer

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

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

What does the example print, and why?

isalnum() — output: True then False

What mistake do freshers make with isalnum()?

isalnum does not change the original string in place.