Validate a Python Identifier

Medium ⏱ 12 min 55% acceptance ★★★★★ 4.8

Write is_valid_identifier(s) that returns True if s would be a legal Python variable name: non-empty, starts with a letter or underscore, and every subsequent character is a letter, digit, or underscore. Implement the checks manually (character by character), without calling str.isidentifier().

Examples

Example 1

Input

s = '_my_var1'

Output

True

Explanation

Starts with underscore; rest are letters/digits/underscore.

Example 2

Input

s = '2fast'

Output

False

Explanation

Cannot start with a digit.

Example 3

Input

s = 'my-var'

Output

False

Explanation

Hyphen is not allowed inside an identifier.

Constraints

0 <= len(s) <= 200

Topics

StringsValidation

Companies

InfosysHCLTech

Hints

Hint 1

Check s[0] with `.isalpha()` or equal to '_'.

Hint 2

Check every remaining character with `.isalnum()` or equal to '_'.

← Run-Length Decode a String Fill In Template Placeholders →

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