Parse CAN Logs for DTCs | Dataford Interview Questions

Write a Python script to parse a CAN log file and extract specific diagnostic trouble codes (DTCs).

Implement extract_dtcs(log_lines, requested_dtcs), where log_lines is a list of log strings and requested_dtcs contains complete DTCs or prefixes such as P0. Decode only frames whose data begins with service byte 43; each following two-byte pair represents one DTC. Return matching DTCs once each, preserving their first-seen order, and ignore malformed or irrelevant lines.

Constraints

1 <= len(log_lines) <= 10^4
Each log line contains space-separated tokens
Valid data bytes are exactly two hexadecimal characters
A service-43 frame contains zero or more complete two-byte DTC pairs after the service byte
Return each matching DTC at most once, in first-seen order

Function Signature

def extract_dtcs(log_lines, requested_dtcs):

Your question is Parse CAN Logs for DTCs. Start with the requirements in the Question tab.

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Problem

Write a Python script to parse a CAN log file and extract specific diagnostic trouble codes (DTCs).

Constraints

1 <= len(log_lines) <= 10^4
Each log line contains space-separated tokens
Valid data bytes are exactly two hexadecimal characters
A service-43 frame contains zero or more complete two-byte DTC pairs after the service byte
Return each matching DTC at most once, in first-seen order

Function Signature

def extract_dtcs(log_lines, requested_dtcs):

Your question is Parse CAN Logs for DTCs. Start with the requirements in the Question tab.

Run and submit as often as you like. When you're ready, talk me through your approach or go straight to the code.