Session Counts from Log File | Dataford Interview Questions

Given a log file where each line is formatted as 'timestamp, user, action', count the number of sessions for each user.

Asked in the Onsite stage as a LeetCode-style coding round focusing on string and log processing. Treat each login action as the start of one session; other actions, including logout, do not create additional sessions.

Input and Output

Implement count_sessions(log_lines), where log_lines is a list of strings. Each string contains a timestamp, user, and action separated by commas. Return a dictionary mapping each user to their number of login sessions. Ignore the timestamp when counting.

Constraints

0 <= len(log_lines) <= 10^5
Each log line contains exactly three comma-separated fields
The action field is a nonempty string
User names may contain surrounding whitespace but do not contain commas
A session is counted only for an action equal to login after trimming whitespace

Function Signature

def count_sessions(log_lines):

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