Python Text Line Counter | Dataford Interview Questions

An Okta System Log export is represented as a list of text lines. Given the lines and a target word, return how many lines contain that word as a contiguous substring, ignoring letter case.

A line is counted at most once, even if the target appears multiple times. Punctuation does not prevent a match, so "MFA denied." contains "mfa".

Formal Specification

Implement count_matching_lines(lines, word):

Input: lines, a list of strings, and word, a non-empty string.
Output: An integer equal to the number of lines where word occurs as a case-insensitive substring.
Do not modify the input list.

Constraints

0 <= len(lines) <= 10^5
0 <= len(line) <= 10^4
1 <= len(word) <= 10^3
Lines and the target contain standard Unicode text
Matching is case-insensitive substring matching, not whole-word matching

Function Signature

def count_matching_lines(lines, word):

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