Python · Intermediate · 45 min

Reconcile account balances across formats

Compare normalized records, not aggregate totals.

Task

Implement reconcile_accounts(source, target). Source rows contain id and amount as a decimal string in currency units. Target rows contain id and cents as an integer. Normalize IDs with strip().lower(), then return sorted missing, unexpected, and changed IDs.

Requirements

Both inputs are lists of dictionaries. IDs are nonempty strings after normalization and unique within each input.
Source amount must be a finite decimal string with no fractional cents. Target cents must be an int, not bool. Negative balances are valid.
Reject invalid input or duplicate normalized IDs with ValueError. Do not modify either input.
Return {"missing": [...], "unexpected": [...], "changed": [...]}. Compare only IDs present on both sides for changed.

ReconciliationDecimal arithmeticNormalization

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