File: remove-vowels-from-a-string/solution.py

Date: 2026-06-06

Time: 18:49

remove-vowels-from-a-string/solution.py

Purpose

This file implements the solution to LeetCode 1119 — Remove Vowels from a String. It owns exactly one responsibility: given a string of lowercase English letters, return the string with all vowels (a, e, i, o, u) removed.

Key Components

Solution.removeVowels(self, s: str) -> str — The single method, following LeetCode's expected class/method signature. It takes a lowercase English string and returns a new string with vowels filtered out.

The implementation is a one-liner: a generator expression filters each character against the string literal "aeiou", and str.join assembles the result.

Patterns

• LeetCode convention: A Solution class with a camelCase method matching the problem's expected interface. Every solution in this repo follows this structure.
• Generator-based filtering: Uses c for c in s if c not in "aeiou" rather than str.translate, str.replace in a loop, or regex. This is idiomatic Python for character-level filtering — lazy evaluation, no intermediate list allocation.
• Membership test against a string literal: c not in "aeiou" performs an O(5) linear scan per character. For a 5-element set this is equivalent to (and marginally faster than) a set lookup due to avoiding hash overhead.

Dependencies

Imports: None. The solution uses only Python builtins.

Imported by: The "Imported By" list in the prompt is misleading — those ~400+ test files don't actually import *this* solution. They each import their *own* solution.py via a relative or same-directory import. The only real consumer is remove-vowels-from-a-string/test_solution.py.

Flow

1. Iterate over each character c in input s.

2. For each c, check membership against the vowel string "aeiou".

3. Yield c only if it is *not* a vowel.

4. "".join(...) concatenates all yielded characters into the result string.

Single pass, O(n) time, O(n) space for the output string.

Invariants

• Input constraint: s consists of lowercase English letters only. The code doesn't enforce this — it trusts LeetCode's guarantees. If uppercase letters were present, uppercase vowels (A, E, etc.) would survive the filter.
• Output ordering: Character order is preserved; only vowels are removed.

Error Handling

None. No validation, no exceptions. An empty string input produces an empty string output — the generator simply yields nothing and join returns "". This is correct behavior, not a gap.

Topics to Explore

• [file] remove-vowels-from-a-string/test_solution.py — See what edge cases (empty string, all vowels, no vowels) the test suite covers
• [file] remove-vowels-from-a-string/review.md — The code review may discuss alternative approaches (regex, str.translate) and why this one was chosen
• [function] reverse-vowels-of-a-string/solution.py:reverseVowels — A related vowel problem that requires identifying vowels in-place with a two-pointer approach rather than filtering
• [general] string-filtering-patterns — Compare this generator approach with str.translate/str.maketrans used elsewhere in the repo for character removal

Beliefs

• remove-vowels-only-lowercase — The solution only filters lowercase vowels; uppercase vowels in the input would pass through unremoved
• remove-vowels-single-pass-linear — The algorithm performs exactly one pass over the input string with O(n) time complexity
• remove-vowels-no-imports — The solution has zero dependencies beyond Python builtins
• remove-vowels-preserves-order — Non-vowel characters appear in the output in the same relative order as the input