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CODE WORKSPACE
To tell whether a record has changed since the last load, you store a digest of its contents and compare. The digest has to depend on what the record says and on nothing else — not the order the producer wrote the keys in, and not which process computed it.
Write digest_records(records, length). It returns one hex digest per record, truncated to length characters.
Function to write
digest_records(records: list[dict], length: int) -> list[str]A list of hex digests, one per record, truncated to `length` characters.
How to approach it
Hash the same record twice with its keys in a different order.
Sample cases
+ 2 held back until you submit
the same record, two key orders
Identical contents must produce identical digests — key order is not content.
Input
Argument 1
[
{
'amount': 12.5,
'buyer': 'amir'
},
{
'buyer': 'amir',
'amount': 12.5
}
]Argument 2
12Returns
[
'2a0de924c96b',
'2a0de924c96b'
]a nested record
Nesting is not special-cased: the whole structure has to be encoded canonically.
Input
Argument 1
[
{
'user': {
'id': 'u1',
'geo': {
'city': 'Pune',
'country': 'IN'
}
}
}
]Argument 2
12Returns
[
'a89337923b47'
]no records
An empty batch produces an empty list rather than an error or a digest of nothing.
Input
Argument 1
[] (empty list)
Argument 2
12Returns
[] (empty list)
Constraints
length hex characters long.None is different from a key that is absent, and the digests must differ.hashlib.sha256, so the digest is the same in every process and every run.Worked example
{'amount': 12.5, 'buyer': 'amir'} and {'buyer': 'amir', 'amount': 12.5} are the same record written twice, so both must produce the same digest.
The starter hashes str(record), which renders the dict in insertion order — so the two produce different digests and every record looks changed on the next load. Python's built-in hash() has the opposite problem: it is randomised per process, so it is stable within one run and useless between two.
What this tests
That a digest is only as stable as its encoding, and that a canonical encoding is a decision you make rather than a property you get. It is also the practical reason json.dumps(sort_keys=True) turns up in every change-detection pipeline.
digest_records(records: list[dict], length: int) -> list[str]Submit for review to find out what your query gets right, what it gets wrong, and how it compares with the best working query for this exercise.
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