A statement to check whether the given character, ch is an alphabet or a number.

Q: A statement to check whether the given character, ch is an alphabet or a number.

**Required statement:** ```python print(ch.isalnum()) ``` The built-in string method `isalnum()` returns `True` if the character `ch` is either an alphabet letter or a digit, and `False` otherwise.

Python Revision Tour

Checking Alphanumeric Characters — isalnum()

Official Answer

Required statement:

``python


print(ch.isalnum())

The built-in string method isalnum() returns True if the character ch is either an alphabet letter or a digit, and False` otherwise.

isalnum()isalpha()isdigit()string methodscharacter classificationalphanumeric checkbuilt-in function

Marking Scheme

11 mark for the correct statement `print(ch.isalnum())`; the equivalent `ch.isalpha() or ch.isdigit()` is also accepted.

Hint

Look for the single string method whose name literally combines 'alphabet' and 'number' — alnum.

Quick Oral Answer

ch.isalnum() returns True if ch is a letter or a digit, giving a single built-in check for whether a character is alphanumeric.

Analysis & Explanation

This question tests knowledge of Python's built-in character-classification string methods.

Why ch.isalnum() is correct

isalnum() checks whether every character in the string is alphanumeric — meaning it is a letter (A-Z, a-z) OR a digit (0-9).
Since ch is a single character, ch.isalnum() directly answers 'is ch an alphabet or a number?' in one built-in call.

Equivalent alternative

The same check can also be written as ch.isalpha() or ch.isdigit(), which combines two separate built-in methods with a logical OR, giving an identical True/False result.

Common Mistakes

1Using only `ch.isalpha()`, which checks for alphabets alone and incorrectly returns False for a digit character.
2Forgetting that these string methods only work correctly on a SINGLE character string when checking one character; on multi-character strings they check that ALL characters satisfy the condition.

Interesting Facts

`isalnum()` returns False for an empty string, since there is no character to satisfy the check — this edge case is a favourite CBSE viva question.

Python's `str.isalnum()` also returns True for many Unicode numeric and alphabetic characters beyond plain ASCII, such as accented letters and superscript digits.

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Frequently Asked Questions

What does ch.isalnum() return for a space character?

It returns False, since a space is neither an alphabet letter nor a digit.

Can isalpha() or isdigit() be used instead of isalnum()?

Yes, `ch.isalpha() or ch.isdigit()` gives the same True/False result as `ch.isalnum()` for a single character.