Python V1 · Deprecated

Solving

Solving in the Python V1 binding.

The Python V1 solving reference continues the Python V1 overview.

Solve

CODE

edb = ruleset.edb()
edb.add_fact('owns', ['alice', 'roadmap.pdf'])
result = ruleset.solve(edb)

result.enumerate_predicate_facts('allow', 2)   # [('alice', 'roadmap.pdf')]

Unlike WASM's clearFacts(), which clears the input after releasing its live result inside one MaelysPlayground instance, ruleset.edb() returns a new, independent object every time — nothing to reset, no session to carry state across by accident. ruleset.solve(edb) finalizes edb exactly once before calling the native solver; after a successful solve, edb is closed for mutation — a later add_fact() raises RuntimeError before reaching C. Calling solve() again on the same, already-finalized edb is allowed and reuses the finalized snapshot; it does not require adding facts again.

Diagnostics

CODE

from maelys_datalog import MaelysDatalogError

try:
    ruleset = engine.load_inline_ruleset('document_access', 'doc.main', bad_source)
except MaelysDatalogError as exc:
    exc.code      # int — last error code
    exc.message   # str — last error message
    exc.hint      # str — corrective hint, empty string if none

hint mirrors the C-level hint field of maelys_datalog_diagnostic_t — see Errors — Diagnostic codes. The current WASM binding likewise carries an independent diagnostic snapshot on its error, instead of mutable instance fields.

Derived fact count

CODE

result = ruleset.solve(edb)
result.derived_fact_count()   # int — total IDB facts derived by this solve

Same meaning as WASM's derivedFactCount() — a property of one solve, not a session constant. A SolveResult corresponds to exactly one solve() call, so there is no "current EDB session" to read it against; call it on the SolveResult returned by the solve() you care about.