PCAP Strings Practice Question

Answer analysis

Option-by-option breakdown

For each option: why learners choose it and why it is or isn't the right answer here.

• ✗

  isalnum()

  Why it's wrong here

  isalnum() is incorrect because it returns True whenever every character in the string is alphanumeric, meaning either a letter or a digit. A string like 'abc123' would therefore satisfy isalnum() even though it clearly contains non-alphabetic characters. The task requires rejecting digits, so this method is too permissive for a pure alphabetic check.

• ✗

  isspace()

  Why it's wrong here

  isspace() is incorrect because its sole purpose is to detect whitespace-only strings: it returns True when every character is a space, tab, newline, or other whitespace separator. Such strings contain no alphabetic characters at all, so calling isspace() on ' ' yields True where a pure alphabetic check should return False. It tests the opposite category of content from letters.

• ✓

  isalpha()

  Why this is correct

  isalpha() is correct because it returns True only when the string is non-empty and every character is classified as an alphabetic Unicode character, covering letters like 'A', 'é', and 'α' while rejecting digits, punctuation, and whitespace. This precisely matches the developer's requirement to check if a string contains only alphabetic characters. Note that it is not limited to ASCII, which is useful for internationalized input.

• ✗

  isdigit()

  Why it's wrong here

  isdigit() is wrong because it checks the exact inverse requirement: it returns True only when all characters are decimal digits, such as '0' through '9' or Unicode digit equivalents, so '2024' passes while 'hello' fails. Since the developer needs alphabetic content, isdigit() could never accept a genuinely alphabetical string and is therefore irrelevant to the query.

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